I don't know what doctor's offices you were visiting, but I was setting up EDI systems inside little hick doctor's offices in the early 1990s to exchange medical records with insurance companies. These were running on DOS machines - and there were probably DOS machines on the other end. Other, bigger offices were more sophisticated, and had Unix systems with multiple terminals. I still have a TI Unix box that came from a doctor's office and was used for medical billing and insurance transactions with Blue Cross/Blue Shield and others. It was decommissioned in 1999 because of Y2K (someone who had bought the right to maintain TI Unix was charging an extortionist's fee for a yearly license for patches to fix the issues - it was cheaper to replace the entire system). Our daughter's pediatrician before we moved four years ago didn't even *have* a fax machine - she probably still doesn't.
I would agree with the OKI printer suggestion - other than power. Maybe there are lower-power versions now. The old ones had a motor that ran constantly, fans, and the print heads would get extremely hot when the printer was busy. I can also say that, while they are heavy and well-built, they are not necessarily rugged - my wife's cat once managed to knock one off a counter and it did not survive (the printer that is - the cat survived; he was just lucky I'm not the violent type - the printer was about $350 to replace).
Cloth printer ribbons can be easily re-inked. Dried out ribbons can be rejuvenated by popping the top open and spritzing the enclosed ribbon lightly with WD-40. When the ribbon has reached the end, it can be popped open, the contained ribbon flipped upside down, and then be re-used when put back together - generally, the print head does not print down the center of the ribbon, so you can get two passes along it without physically using the same strip of ribbon this way, reducing wear. Once you've done that a time or two and the ink starts to dim, the WD-40 trick also works to re-distribute the ink inside the ribbon material. I could usually get around six passes through an OKI ribbon before it needed to be re-inked.
I gave away my last two OKI printers to a school about six years ago. They were probably at least 15 years old then, and are probably still going.