You could contact jayco customer service and see who the manufacture is and see if you could get a replacement piece, but the best option would be to google a local custom glass shop and have them cut you a piece and install it in the frame.
I installed the plastic sliding door in my last RV instead of a shower curtain. It worked well and my wife liked it. My shoulders don't give me much room and I'm always knocking the glass in the Greyhawk. The plastic slider was a little more tolerable. Two things I don't like about the plastic slider are:
1) if you loose your balance don't plan on the slider helping at all as you'll go right though it
2) rarely it would come unhitched and slam shut (springs rolling in the plastic like a drape rolling up on a window) while taking a shower and water start going everywhere. I think it was a magnetic latch.
If you go with a local custom glass shop, make sure its tempered glass so it breaks into small squares instead of jagged pieces.