Kodak Retina soft release

Hiya. I just noticed that the little metal cap that would normally be on top of my Retina II shutter release has decided to disappear forever. It's not a standard thread (the cable release socket is separate to the shutter release) so a regular soft release button won't fit.

Has anyone found a good substitute for this? The button is pretty damn sharp and unpleasant without the cap. Is there an easy way to measure a screw thread to potentially use a large headed screw?

The most simple way would be to test that thread out of a range of screws. The thread most likely is a metrical one, maybe with fine pitch.
That screw then can me measured on diameter with a caliper and tested on pitch with a pitch gauge.

An alternative may be grinding off the rim of the release button or putting a resin cap onto it, from epoxy glue.