Need a new cellar

My 20+ year old Vinotemp cellar has just burned out its second cooling unit. I had a hard time finding a replacement about 6 years ago when the first unit died, so I suspect it's time to get a new box.
I don't have room in the house for it, so it'll have to go in the garage; therefore, appearance isn't a problem.
I need to hold about 250 bottles in it. I've been Googling but haven't stumbled across anything.
I'm in Sonoma County, so it's warm summers and cool but not freezing winters, and the garage is an old stand-alone uninsulated building.
Any ideas?

You might want to consult a HVAC professional about using a commercial refrigeration unit of the kind they use in supermarkets. Unfortunately the units used in a lot of consumer wine cabinets are the same sort used in room air conditioners. They are not designed to operate at the low temperatures of a wine cellar and because of that they burn out prematurely.

-Paul W.