For sale is a Phase One Contax 645 Insert Plate that will let you mount your Contax 645 mount digial back on a Phase One Flex Adapter. I believe it will also work with the Linhof Sliding Adapter, but please do your homework!
Ideally, I'd like to do a straight trade for a similar Hasselblad V, H or Mamiya mount insert plate. If not, it is for sale for 18,000 JPY / ~170 USD, including worldwide EMS shipping. Payment is in Japanese Yen, payable via Paypal invoice or bank transfer through TransferWise, which will save you ~4%.
Thanks for looking,
Kumar
