I'm not familiar with rack mount cabinets...but wouldn't it be possible to just buy 12VDC 120mm thermally controlled fans, and get a 12V power supply?
Marlin P. Jones and Associates has a good selection of power supplies; I've ordered from them a few times before; no complaints. You can also check out
All Electronics and
Electronic Goldmine. Those are two other companies I used to order from; I don't much anymore - I shifted away from electronic gadgets to PC's. I do order from them sometimes though; the only "issue" with these stores is that they deal partially with surplus, so some things may be sold out - when you place the order, you need to tell them to hold shipment if anything is out of stock, and contact you for instructions. Otherwise, they will likely just ship it without the sold-out item(s).