What size serpentine belt do I need to by pass the AC compressor?

Unplug the wire connector at the compressor clutch coil.! That will disable the compressor and then it becomes just an idler for the belt! .. That should work as long as the pulley bearing is ok!!

I just did this on mine; youtube has a few videos that show the routing of a shorter belt and how to move the compressor up out of the way. if you leave it as suggested the pully can seize up and that could be a big issue while driving mostly losing the power steering. the comments in the youtube replies suggest the belt size to get (at work now so don't remember offhand). it was pretty simple to do took less than an hour with basic tools and im no mechanic, good luck.