I usually deal online with either a credit card or PayPal. I've bought a lot of parts and stuff from StewMac over the years without any problems at all. And I live in Canada, so everything I do is an 'international incident'! :)

I've also dealt with
Torres Engineering
1630 Palm Avenue
San Mateo, CA 94402
Phone (650) 571 6887 Fax (650) 571 1507 Pacific Time 10:00AM-5:00PM.
online quite a few times, and had good experiences every time - including my purchase of a flood-damaged VT-40 during a scratch'n'dent sale they had a few years ago. That involved arranging to ship 95 pounds of combo amp from San Mateo California to Calgary Alberta! I have read a few BBS comments to the effect that Dan Torres can get a bit testy when things go off the rails, but I've never had a problem.