I agree that anywhere is a good place to start. That said, I found the prices on FAK supplies to be just as reasonable if not better at the local Target. In fact, there was a promo coupon last year where a starter kit could be had for a mere .22 cents.

Myself, I began with a little freebie first aid pouch I got from a mechanic's shop many moons ago. Something like this:

http://www.epromos.com/product/8833294/custom-zippered-kit.html

Great idea if you have a business to promote...