Well I ended up bidding on two TP-10 printers on eBay, and they arrived while I was away at Hamvention.
The first came with a 4 pin din to DB-25 cable and appears to have been rebanded “MAGTEK MCAT Printer” although the bottom still shows Radio Shack TP-10, I wouldn’t be surprised if the TP-10 label is below the MAGTEK sticker.
The other TP-10 came with a box, the Styrofoam, the 4 pin serial coco cable and some paper!
Good News both of them work in self test and connected to a Coco 3!
Cocoman's Blog 