I have done it with a hole tapped M3 (small hole, under 1/8"). Advantage is no paint touch-up needed.
I used an adjuster screw from a horizontal dropout, cut the head off to have a very short piece of "all thread", and threaded on the knurled nut that Campy and many others used on those adjusters. With Loctite, natch.
Campy at some point (~1980?) stopped using a metal nut, switched to a plastic abomination, so definitely get a metal one. They were made by plenty of others too like Suntour, Gipiemme, Tecnociclo etc.
The look is not objectionable with the pump off, and of course disappears when the pump is installed

I don't have a bike with that now, so no pics.