I've observed that Pertec-to-SCSI adapters are
even harder to find
than PC interface cards. The PC cards come up about every 2-3 months
on eBay, but mostly without drivers. I think I've seen exactly one
SCSI-Pertec protocol converter in the last year--and the minimum bid
was about $200.
Here's a little secret, since I probably have enough of them now.
Every Qualstar 1054 has a pertec-scsi bridge board in it. Early ones
used NCR, later ones have their own design.
The last couple of 1054's I've picked up on eBay were MUCH less than $200.