I would look at VID's Guide to Cleaning and Waxing Pinball Machines - a good place to start.

https://pinside.com/pinball/forum/topic/cleaning-and-waxing-pinball-machines-vids-guide

Maybe try locking pliers (szczypce blokujące?) on the end. I would use some WD-40 penetrating oil on the bolt first, let it soak in for 15 minutes.

In my opinion, very good, I am quite happy with it, very noticeable difference over the translite.

I know you are looking for NOS, but if you can't find it, CPR has a nice reproduction set available.

That is a very nice looking Pinbot. I can't keep up with today's pricing so I wouldn't hazard a guess, but Pinside recent sales seem to be in the $3,000 -$3,500 range for nice examples, probably not as nice as this one. Glad I got mine when I did

Edit: Should have looked at the other posts first, more of the same here...

Several to choose from:
Comet for lights https://www.cometpinball.com/
Or order through Pinball Life https://www.pinballlife.com/storefront.html
Or Marcos https://www.marcospecialties.com/control/main
Or, a little harder to use but a great resource Steve Young Pinball Resource http://www.pbresource.com/
and for Pinbot specific parts, Planetary Pinball Planetary Pinball https://www.planetarypinball.com/

These are all legitimate, long time businesses. You will probably be ordering a lot of stuff through them over the years - welcome to the hobby!