Temporary fix that also preserves originality would be to build up top of safety slide with epoxy putty to form a ramp for your thumb to push against.

It should break away fairly easily if you want to get rid of it.

Mind you don’t get any under the safety!

I have used it to build up, filing it to shape and right height, then painting Matt black, to raise the military barleycorn front sights of a couple of Martini carbines that shot very high at 100 yards.