what's the thinnest pusher fan you've seen, and who makes it? Im just looking for a small one for an auto. trans. cooler, but I need a very this one.

try looking around i know perma cool is one of the best companies they have some in the 2" range

Summit has a cooler with a fan already mounted on it. It's made by perma-cool and the small one runs 172.95 (4"Hx10.5"W x18"L) part# prm-13315. The larger one runs 183.95 (4"Hx10.5"Wx21"L) part# prm-13318, both units flow 1250 cfm.
If you are looking for just a fan they have a 7" fan made by derale that flows 400 cfm and is 2.55" thick for 67.95 part# der-16507