Just keep doing what you are doing, if you wind up with the grub screws wearing out, I believe you can measure them with calipers or even just looking at the specs and well, if you aren't stressing them you won't overstress them, but if it makes you feel better you could probably buy the same or similar grub screws that will work elsewhere, it doesn't have to be direct from the manufacturer (or even identical) honestly. Lots of folks replace the screws in the Doggy style with screws other than the flat head screws because they are so dang annoying to work with. One day, I may be among them.
I usually just shove mine at the husband and he tells me what to get and/or if he can procure me something that will work. Yes, I have it easy.
Similarly with the O rings, you might not wind up with an exact 1:1 convergence should you ever need to replace them but well, it sounds like you may not need to replace them.
Anna