I've seen some teeny button switches on the MK Jam forum recently. I wonder if one of those could be persuaded to fit? I think it would still have the same issue with distance between the legs though.
What's needed is a momentary switch with inside leg measurement of 2.54mm
I wonder if such a thing exists?
You want it to stick up just enough so you can press it intentionally, but not so much that it'll be easily possible to press by accident. Putting something on top of a normal height header, would be too high. Although there is still the "touch a metal object briefly to the header" option with just a normal header.
If you were feeling super silly...
(No - hold that thought - I've just had an idea for my next video