I've heard this is a good regulator also but you'll need to pick up a solenoid and needle valve to go with it.

VICTOR 0781-1123 CO2 FLOWGAUGE REGULATOR MIG TIG - eBay (item 260210049655 end time Mar-08-08 07:20:03 PST)

I've had this one for over a year with no problems.

AQUARIUMPLANTS.COM's Co2 Regulator)