score:1
The Catholic Bible on NewAdvent.org says that there is no exact match in known scripture.
HOLY BIBLE: John 7 says this:
On the last and greatest day of the feast Jesus stood there and cried aloud, If any man is thirsty, let him come to me, and drink;
yes, if a man believes in me, as the scripture says, Fountains of living water shall flow from his bosom.[5]
He was speaking here of the Spirit, which was to be received by those who learned to believe in him; the Spirit which had not yet been given to men, because Jesus had not yet been raised to glory.
…
[5] ‘His bosom’; it is not clear whether this refers to the believer, or to our Lord himself; the old commentators are not agreed. In either case, it is impossible to trace these exact words in any passage of scripture as we have it; cf. however Is. 44.3, Zach. 13.1. Some would punctuate differently, with a full stop, instead of a comma, after ‘believes in me’.
That Jesus was paraphrasing the scriptural imagery is a reasonable conclusion, regardless of one's denomination.