"Your local shop is feeding you a line of BS. Go to the link below to find a parts list for your model refer.
Norcold Inc. Refrigerators
I found this comment interesting. I had the seals replaced under Norcold's extended warranty by a service center I use. I thought that he'd just replace the seals, but he replied basically the same as the OP's service provider did, "complete doors, seals not available." Norcold sent new doors freight paid and paid the labor. When I checked the link given above I see no breakout for the seals. In case my seals fail again is there a part number for the gaskets that I'm missing?