Upvote:2
You'll want to go to the Peruvian Embassy in Buenos Aires.
The cost of a tourist visa should be US$30, and it should take at least 24 hours (can probably pay more to get an express one).
Requirement for Peru visa application: Those requiring a tourist visa must provide:
The address for the embassy: Peruvian Embassy Av.del Libertador 1720 1425, Buenos Aires
(source)