I'm an engineer by trade, and hobby, I love to make things. So when I saw what could be done I searched my workshop for something that I could use, but I didn't find anything so I made it.
The sort of thing I was looking for was a bearing shim, like you might find in a car wheel hub to set the bearing end float. I had plenty, but not the right size.
A quick Google however turned up this site -
Ondrives: Bearings - Ball Bearings - CPS - Precision Shim Washers - 52-56mm Bores
which has shims in all sizes, this page actually lists a 52mm i/d, 65mm o/d by 1.5mm thick shim, but they sell them by the hundred.
Over here I use local engineering suppliers that carry these kind of things and sell them singly.
So, if you can measure the size you need you might find your local engineering supplier becomes your friend.
I was also thinking that if a washer was used on a lens without the recess like the Takumar has, and it pushed the lens forward by maybe 1.5mm then it would lose infinity focus.
But the chances are that if you wanted to use focus trap you aren't focusing on infinity anyway. And the washer is removable when you want infinity.
problem solved, send all your donations to me!