I've bought all my flash carts from Stone Age Gamer. They gave me a free SD2SNES for creating SNES bitbox covers. I "purchased" it for free through the site, which also earned a bunch of tickets, which I've been rolling forward ever since.
Edit: SAG has given me great customer service and warranties everything, I plan on waiting to buy SSD3 when they carry it as a US retailer, rather than deal with international payment problems.