CompUSA has the BFG Tech GX-550 550-watt modular power supply: http://www.compusa.com/applications/searchtools/item-details.asp?EdpNo=3942984
for $30 + shipping. I believe this is a modular form of the GS-550 (not
quite as good as the LS-550).
Just picked up two for some simple builds. Not bad for some very decent
modular power supplies.