The easiest and simplest solution:
find grub screws that are wider, BUT which use the same key!
Gong sell some
www.gong-galaxy.com/produit/gong-vis-de-remplacement-plug-abime-la-paire/ but of course you may find some locally
I have repaired some holes by:
- roughing the hole by making small lengthwise grooves to avoid the filler rotating with the screw
- filling with a very hard material: epoxy resin with a lot of microspheres for me, but metal fillers should work
- waiting for complete cure (many days, gentle heat helps)
- drill & tap
By the wider screws are just so convenient. Buy them in advance and keep spares in the car!