Schimel...Please Help!

Hello Everyone! I'm new here so be patient. I recently purchased a Schimel GP22. The Co2 cap was frozen in place. I managed to remove most of it by drilling a hole, and Turning out the rest on a Lathe. What I need is a replacement Plug or Threads Per Inch Spec. If anyone can measure the Thread Pitch and LMK, I would be VERY Thankful.