boxhead
Sorry to chime in here on the FL site, but have you considered drawing one onto the body and then getting the local metal shop to make one up.
The frame/ring screws down into the body in four locations using button heads and nylocks. Use about six nylocks to attach the perspex screen to the frame/ring.
Take the perspex off the ring and you can put your normal screen back on. If you want to run one..
Perhaps talk with Aussie Mike if you have no luck here.