Once you have an idea of the length and width of the release pin it's not too difficult to make one. You sort of rumble through the tool box, or go to the hardware store and look for a suitable piece; a nail, pin or similar metal piece you can cut off just the right length. You can search up any
replacement part though, some specialize in older sewing machines.
There might be two different release pins for model 66, I'm not sure. The older version tensioner has a simple nut you adjust the tension with, the later version has a numbered dial the same as you 201. Double check you get the correct type.