I'll tell you what I would do, if only temporary. WHAT did you have it working with? (What OS?) If you look around you can find older, working laptops, with real 9 pin, real parallel port (printer) ports, etc, with Windblownup sleven, Whinhozed XP, etc etc. You just have to look. Might even put up a want ad
I come from the world of amateur radio, and for a time worked for a Motorola shop, up near 2000. Even back then, we COVETED older machines that could be used for radio programming, in some cases, old DOS machines, AND I STILL HAVE ONE.
I don't know what all you've tried. Have you gotten the / some/ one of the adapters you have to work with other hardware? That would at least show "end to end" success on the adapter/ computer.