A couple of years ago a member brought up the subject of controllers. Here is the link to that post.
https://www.pro-pinball.com/forum/viewtopic.php?f=23&t=95
In that post, that poster talks about the, " crazy French keyboard with pinball flipper buttons". The poster offers a link but the link was/is dead. The keyboard is called Keyflip. And I am the one in that post who replies that I own a Keyflip. I bought it in 1998. It is a fantastic way to play desktop Pro Pinball.
I am bringing this up because I recently found a live link for where you can still buy a Keyflip to play your Pro Pinball sims.
The Keyflip link had a current email address that I contacted. The owner/inventor of the Keyflip, Jean P. Auderbert, replied that (after 18 years) he still has about 100 units left to sell.
The connection is PS2 but I have been using a PS2 to USB adaptor and played Pro Pinball on my old Macs and my XP PC without problems. All the keys are programable within your old Pro Pinball games except for L and R buttons for up-nudging. Pro Pinball did not support that so I used the space bar for up-nudging.
His price is 65 Euros with shipping included. Plus, it looks a free copy of the old Timeshock still comes with the package. He speaks French only, so to communicate you might have to use a web translator.
Here is a good link to his website.
http://www.keyflip.fr/
Here is You Tube video of the Keyflip in action.
https://www.youtube.com/watch?v=_81qXsR_5UE
As I stated, he only has about 100 units left to sell. I don't think you would be sorry if you bought one.