Are there any references to "four canonical Gospels" prior to 100 AD?

I am not sure I'm understanding the question. I see two possible things you might be asking...

I don't know about evidences of others calling them the four Gospels (not sure that's exactly what your last sentence is asking), but there is first century manuscript evidence for at least some of the Gospels.

There is potentially evidence for the book of Matthew in a few fragments, but the dating of it is a matter of debate. The original, cursory examination gave them a date of the forth century, but a later examination gave them a date of A.D. 66.

From http://www.equip.org/articles/eyewitness-to-jesus-amazing-new-manuscript-evidence-about-the-origin-of-the-gospels/

The Matthew fragments redated by Thiede are at Magdalen College (Oxford). They are called The Magdalen Papyrus (listed as Greek 17 and p64). There are three fragments written on both sides, together representing 24 lines from Matthew 26:7-33. Two of the three fragments are a little larger than 4 x 1 cm.; the other is smaller, 1.6 x 1.6 cm. Another two fragments, located in Spain, are called the Barcelona Papyrus (P. Barc. inv. 1/p67) and contain portions of Matthew 3:9, 15; 5:20-22, 25-28.

Also, while less specific, faithfacts says...

Early fragments: John Ryland manuscript 130 A.D. in Egypt; Bodmer manuscript containing most of John's gospel 150-200 A.D.; Magdalen fragment from Mat. 26 believed by some to be within a few years of Jesus' death; Gospel fragments found among the Dead Sea Scrolls dated as early as 50 A.D.

Several other sites list the Dead Sea scrolls dating to the first century A.D.

DTS lists another fragment dating to the first century.

Dr. Wallace: Earliest Manuscript of the New Testament Discovered? by Daniel B. Wallace on February 9, 2012 in Articles

Note: Several websites (NT Blog, Gospel Coalition, Andreas Köstenberger, Evangelical Textual Criticism, Hypotyposeis, etc.) have been writing about Dan Wallace's comments to Bart Erhman about the discovery of several New Testament papyri. Dr. Wallace has already written a summary of the debate, and below he clarifies what these papyri might mean.

On 1 February 2012, I debated Bart Ehrman at UNC Chapel Hill on whether we have the wording of the original New Testament today. This was our third such debate, and it was before a crowd of more than 1000 people. I mentioned that seven New Testament papyri had recently been discovered—six of them probably from the second century and one of them probably from the first. These fragments will be published in about a year.

These fragments now increase our holdings as follows: we have as many as eighteen New Testament manuscripts from the second century and one from the first. Altogether, more than 43% of all New Testament verses are found in these manuscripts. But the most interesting thing is the first-century fragment.

It was dated by one of the world’s leading paleographers. He said he was ‘certain’ that it was from the first century. If this is true, it would be the oldest fragment of the New Testament known to exist. Up until now, no one has discovered any first-century manuscripts of the New Testament. The oldest manuscript of the New Testament has been P52, a small fragment from John’s Gospel, dated to the first half of the second century. It was discovered in 1934.

Not only this, but the first-century fragment is from Mark’s Gospel. Before the discovery of this fragment, the oldest manuscript that had Mark in it was P45, from the early third century (c. AD 200–250). This new fragment would predate that by 100 to 150 years.

Getting back to the distinction I mentioned in the first few sentences of this answer...

If you're not asking whether we have manuscript evidence from the first century, but rather writings establishing Matthew, Mark, Luke, and John as the only canonical gospels....

I don't know that we should necessarily expect the early Church to refer to the four "canonical gospels" in that way. The way canon was established was at least partially on establishing what the established, trusted writings were. The best we could hope for is to establish whether the first century Church accepted these writings, and whether they interpreted this to mean that these four, and only these four are acceptable as canonical (thereby excluding others. For that, we have no evidence, but that is more likely because it wasn't until later that they became concerned with formally establishing canon.

From http://www.churchhistory101.com/new-testament-canon.php

A Natural Delivery

• The NT was NOT dropped from heaven.
• The NT was NOT delivered by an angel.
• The NT was NOT dug up in a farmer's field as golden plates like the Book of Mormon.
• The NT was NOT suddenly "discovered" in a clay jar with 27 "books" intact like the Dead - Sea Scrolls or the Nag Hammadi texts.

The NT canon developed, or evolved, over the course of the first 250-300 years of Christian history. If the NT had been delivered by an angel, or unearthed as a complete unit it would not be as believable. Part of the historical validity of the NT comes from the fact that we can trace its development, albeit not as precisely as we might like.