I've tried looking for the NA SSC 3.0 too.  Fruitless effort.  I've seen at least 2 pop up on Ebay BUT 1 problem - 
The Seller uses PayPal.  I no longer have PP due in part to the company not notifying me that they were cutting off my services without my knowledge or permission.  I want nothing to do with those bastards again.
So I sort of feel screwed over, that's why I'm looking around for a converter that will enable me to use the PC Engine 3.0 card.  At this point, I'm willing to pay around 100, maybe more.