Answers like yours do help.
End users have to support users directly on subjects that are off the beaten paths (but still very valid questions). As you can see in this thread, you tend to not get much but negativity from those that don't understand that not everyone has the money to spend on new peripherals.
That being said, I did find a used, but functional, Spacemouse Pro on ebay for under $100. I also recently dug out my old Spaceball 4000 FLX that I used with very early versions of Autodesk Inventor (and an Inventor competitor back in the day) and researched a way to get it working out of curiosity (and a quest to not spend money that I'd rather not spend). A regular USB-to-Serial will not work, as then you need the drivers and new drivers do not support the 4000 FLX in modern versions of Microsoft Windows (even if you did get the USB-to-Serial adapter working)...but an intrepid user created a way to do this with a bit of patience, a tiny bit of soldering, a smidge of electronics know-how (or willing to learn), and an arduino board with accompanying other bits:
https://www.instructables.com/SpaceBall-4000-Serial-to-USB-Adapter/
It allows a Spaceball 4000 FLX to emulate a modern Spacemouse Pro. Not perfectly (there's not a one-to-one button mapping), but close enough for hobbyists.
This is totally NOT supported in any form or fashion, but if someone has this old hardware, 3DConnexion made these things to frickin' last and driver-based obsolescence was almost the only way they could afford to stay in business (hard to sell new stuff if the old stuff just keeps working). I can't fault them for having a forced obsolescence in that context one bit, but it's hard for a poor hobbyist to throw out hardware that's made as well as these old 3D controllers just for lack of a modern driver. The Spaceball 4000 FLX was a game-changer in 1999. Before that existed, 3D controller systems were only available at places like super-large design firms for $10k+ (which is a LOT more adjusted for inflation).
Along comes Autodesk Inventor in 1999 and suddenly actual parametric design was available to the masses followed closely by controllers like this in late 1999.
Keep posting solutions like you have, my friend. Pundits and corp employees legally can't provide guidance because they have to recommend hardware that is officially supported (and I don't fault them for that due to liabilities and don't think it's personal, because it's not)...but third-party consultants could be a bit more sensitive to budgets and at least be nice about it (I would think, anyway).
Just my $0.02.
Happy CAD-ing!
