Well, if you can do it without damaging the frame....
No pictures so it's hard to "see" how damaged the screw head really is.
Some things I've seen/heard of others doing:
1. take the next sized torx screw bit and use a hammer to tap it into the damaged hole in the screw. I have done this with allen head and torx screws and gotten messed up screws out.
2. find something you can use (depends on how much damage there is to the screw head) to "fill in" the hole/corners/edges between the screw tip and the hole in the screw, put it over the hole and tap the correct sized torx bit into the hole. I've used steel wool and aluminum foil both.
One time I even epoxied the bit into the screw with some of that metal repair stuff (can't remember the name of that stuff right now, but it's the stuff they advertise even using to repair busted engine parts. Just be careful not to get it on the pistol surface.
Be sure to lay the pistol on something firm, but covered with a cloth so you don't damage the frame surface (scratch/gouge) while tapping on the screw to drive it into the screw head.
Good luck with it.