Mount pinhole to Polaroid MP-4 shutter?

I have a shutter assembly for a Polaroid MP-4; it has Copal 1 sized threads. I'd like to mount a metal disc with a pinhole in the center to the shutter. I tried using a M40x0.75 filter adapter, but its threads are too short to catch the inside of the shutter.

I was going to purchase a shutter cap from Rafcamera (https://rafcamera.com/cap-m40x0-75m?srsltid=AfmBOoq6UT7Fqopl8Lghyul16oPopDjh9OWfRXusdCTGk5O26EOMUOXw), but the cost of shipping, and their disclaimer about the delivery time made me uncomfortable..

Can anyone suggest a non-destructive way to mound my pinhole disc to this shutter?

I've mounted pinholes into shutters by the simplest possible method: I taped the pinhole into a card stock disk (black, of course) cut to a drop-in fit for the front thread of the shutter, then built up a collar around the edge of the disk with black masking tape (gaffer tape would probably also work, though you'd need more clearance at the disk edge since the tape is thicker). The result is like a shallow cup with the pinhole in the center of the bottom; I just push this into the shutter thread. I've used this on my Ideal plate cameras and it's similar to the permanent mounting I put in a 3-speed Vario to go on my electron microscope camera shell for use with 4x5 Graflok accessories.

I cut a circular bit of cardboard that is a reasonably tight press-fit into the camera/shutter. The best cardboard that I have found is from Ampad 'Gold Fiber' legal pads; I imagine an art supply store would have a good selection of suitable card stock. I don't use any extra tape, the press fit is light-tight enough.

Ooh. that's a good idea for those shutters if one is lacking appropriate lens cells.

Thank you all. I like the idea of the cardstock or cardboard. But I'd really like to puzzle out something a bit more robust (and to use my elderly MP-4 shutter for a change!).

It's been a while, but I've made some progress.

I started with an MP-4 shutter with a missing slow-speed escapement (a long story), a 0.4mm pinhole in a 2" aluminum disc, an M53 x0.75 Female to M40 x0.75 Male Thread Adapter Ring (both purchased from eBay) and some black silicone sealer:




I glued the pinhole disc to the adapter:




...then mounted the adapter to the MP4 shutter attached to my Crown Graphic:




It's far too windy to do a proper test, but I was able to get this Instax Wide shot at a six second exposure:




Nothing special, but a good proof-of-concept.