B&H Photo in NY 1-800-947-6628 www.bhphotovideo.com
Free StyleCamera in LA 1-800-292-6137 www.freestylecamera.com
I'll second Pam's mentioning of these two, not familiar with Porter...
A few items such as "Stop Bath" will hit you with an extra fee for shipping
a hazardous chemical. About $4 (if I recall) for the little concentrated
bottle, and about $15-$17 to ship it! I get my digital photo paper from
Free Style as well.