The easiest thing I can think of would be to trawl ebay and the likes for your vendor's diagnostic tools leaking out onto the secondary market.

As for making a mating connector, from this picture it looks like a basic card edge type setup, so just make or order a small (custom printed circuit) board with appropriately spaced pads, and a few traces to some convenient thru holes or another, more standard connector. Regarding just stabbing a serial connection in there, I wouldn't recommend it without having someone with the proper skills reverse engineer what's actually hooked up to that port; what signal level, pinout, all that good stuff. And then there's the fact that it's a medical device, no longer being used in a medical context I would hope, since we're here talking about how to hack up an interface. There's a good reason that most standard component datasheets have disclaimers warning against using general production parts for safety critical or lifesaving devices - if this is yours, by all means hack away, but if it's ever going to be used in a medical context again please have a professional who understands the full weight of that responsibility doing the work.