Need some info about USA receipts

I intend to buy a Dreamcast at eBay, but for taxes reasons I need a legal receipt of the purchase, with the actual value of the system, not the original value. I was wondering if it's easy to get one of that in the US (since I'll probably buy from someone living there).

See, the thing is, I live in Brazil, and here I can't pick up a Dreamcast at that price. Even with the shipping, it's still cheaper to buy at eBay, but I can only do that if I can get a legal receipt for the usual brazilian bureaucracy.

If anyone knows an online store that sells Dreamcast for good prices, it'd be nice too.