West Systems is awsome stuff and they sell a lot of varieties...just don't tell them you are "building planes" with it, they may have a fit.

I have also found some really good stuff at Home Depot and Lowe's...big containers too, not just the little tubes, but pint cans (quart kit).

The best by far is Aircraft Spruce and Specialty- www.aircraftspruce.com

They have a huge variety of epoxies/adhesives (T-88 structural adhesive is a mega strength epoxy and it cures down to 35 degrees F- in fact it's made for builders of homebuilts who live in cooler climates) and the prices can't be beat- except on the CA they sell, it's not cheap and the same stuff you buy in the hobby shop.