I would take your microphone into your local ACE and see if they can help you find the right size
Are the threads on your screw stripped?
This guide was done as part of the capsule replacement—I don’t think there is any reason to solely replace the plate unless there was corrosion on it.
Honestly, I’m not sure. If I was in your position, I would assume a similarly sized piece of electrical tape should be fine, but if you’re not sure you may want to contact a repairman.
Are you trying to disassemble or reassemble the microphone?
It's been a few years since I made the guide and no longer have any microphones nearby to examen, but if I remember correctly, there is no soldering between the capsule and the housing. I believe the housing is soldered to the rest of the body with the silver leads at the bottom left of the picture.
I'm not familiar with the "pin 2 hot method." We took a working mic apart and reassembled it the way we found it, so I'm pretty that is the correct soldering configuration.
I couldn't tell you without looking at the mic, however I am sure you could find the answer by googling it and reading through forums. What exactly are you trying to do to the mic?