Keep looking and be patiet. "B" power supplies occasionally are given away for free. Someone has the power supply for your enlarger and is using it as a paper weight. I got a free "D" power supply a while back. The unregulated power supply is just a transformer in a box and there is not much that can go wrong with it.
Also, you can get a generic 75w supply from a number of sources. The pins are slightly differnet on the 120V dichroic lamps, so if you go that route you will need to replace the lamp socket (not a bad idea in any case).