by Aratus » Fri Mar 04, 2016 6:09 pm
That's the point the OP was making - he doesn't know where to get them from. I think they might be used for certain instruments, interferometry etc. Clearly the author of the article knows where to get them from, but I've not come across them.
Your idea with the ball bearing sounds a lot more feasible, and a great deal easier to obtain the parts. How it compares to the one mentioned in the article though, I couldn't say.
You can find ready made ones for about £60, but for best results they always recommend the telescope be about 100ft away from an artificial star. My back yard is just a little short of that.

I use an 11" reflector (Celestron CPC 1100) and a 3" refractor, (Sky-Watcher ST80) mounted on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI 120MM, ZWO ASI1600MC and Canon 1300D for imaging.