Kaiser Cable Release Adapter (L Shaped)

You're going to need an extension designed for recessed lens boards like the one that Gepe makes. I'm guessing you're asking about this one because the Gepe extension is hard to get (currently has been out of stock for a while at the time of your asking). With this Kaiser angled one, I measured and you'd need something like 32-35 mm of clearance with your particular use.

Yes, the Kaiser Cable Release Angle Adapter (L-Shaped) would be compatible for use with the Mamiya 7 medium format camera body.

It has an angle of about 100 degrees (it is not an exact 90 degree right-angle). The female socket measures 4.0 mm externally and about 2.0 mm internally. The male screw/post is the same, tapered from about 4.0 mm maximum down to about 2.0 mm minimum. The length from end to end, and going around the angled corner, is 2.85 (72.5 mm). The average width of the adapter varies from 4.0 mm to 3.0 mm in diameter depending on the location of the measurement. And finally, the overall height of the adapter from top to bottom in any direction is 1.61 (41 mm).

While not tested specifically, we see no reason that this would not work with the Leica M7.