Check cars.com. I just picked up my '04 with 4000mi on it from a lead on that site. There were several other red Vipers listed there as well-low miles 05's and 06's. I probably went at it with the wrong philosophy, but after looking at the '04's, and finding out that it is basically the same as the 05' 06's, I opted to save about $10,000.00 and go with the '04 and some mods right off the bat.
Good luck in your search-I've had mine for two weeks now and wish I would've gotten one YEARS ago!!