If it was smoked plexi, a slider type, the original equipment manufacturer was Viplex in Sarasota, but I understand they've been merged or bought out over all these years. They also made several other plexi/lexan products for the Scarab models like wind deflectors and wind shields.
I might be able to get a pict of it tomorrow when I go down to the boat to open her up for the season. It uses a hook & eye to stay open, and an unusual latch to close.
I never bother to latch it closed, or lock it up. There's no point letting a moron smash a $1500 door to steal a $200 stereo.

Perko probably made the latch, I'll see what mine says.