ugh,i commend you on going the route of wiring a jamma,i wouldnt touch those things with a 10ft pole after reading all the headache it is of converting. Good luck!as for plexi, call SWS hardware,you can get a sheet for around $570,currently cheapest in the country.Thats the thinnest ones though,and its 5x8 sheet.
I don't really understand most of what you are doing but keep it up