You won't find a "new" WS board for sale with the BSMT2000 unless an op has a NOS one sitting on a shelf somewhere.
K's Arcade sells the later WS which emulated the BSMT2000 as new for $455.
Even then, I'm not sure it will work 100% in your machine as the emulator is just that. I've seen many reports of people having problem with the Xilinx in the early WS machines.
Doubt you will find a much better deal than what Joe is offering above.
viperrwk