Here is a photo of the original board:

These rarely show up for sale, and if they do the sellers are asking crazy money.
There are two models of these boards - the 12 Voice and 24 Voice.
The 12 Voice card is basically the same as the 24 voice except there are 3 DSPs and support components missing.
Presently I'm estimating the re-created 24 voice card would be around £180.
Would any Supernova II users be interested in a 24 Voice expansion at that price?
As a side project I could offer an upgrade service to expand the 12 Voice card to 24 voices for around £80.
Brian