Here is the link for eBay:
DETOMASO PANTERA 71-74 PARTS: INSIDE MIRROR AND BRACKET | eBay
I am going to print the base myself once I get to that point. I was able to dis-assemble the mounting on the new mirror. Also looking at creating a new bracket on the 3-D printer to adapt to the original mounting base. Not sure which way I will go at this point.