OK, I thought I could see a knob in one of the pics in your first post.
An 8mm hole in a 1/2" bolt would be no problem on a lathe, as long as it's accurately cenred, I think it will leave plenty of wall left on the bolt for the application. I think it will be hard to get a really accurate hole in a drill-press, but I don't suppose it would matter if it were a few thou off-centre as far as its function goes.
PM or email me, & we'll sort something out - the whole job, drilling out the bolt & making the brass pad would take less than a 1/2 hour, even on my kindergarten lathe...
Cheers,