If you're seeking a PS3 under or at 3.55 FW...your best bet is to start with pawn shops so they can boot it up and you can verify the FW before purchasing.
Buying new.....that's a little tougher unless you get a PS3 that's bundled with a game but not with the PS Move.
See here:
http://www.ps3hax.net/showthread.php...ighlight=guide