I'm resurrecting this old thread to update the information I found today.
The only replacement part I have been able to find for the Tub-Master folding shower door is the rollers used at the top and bottom tracks. The panels, hinges and other components are no longer produced.
The least expensive price I found for the rollers is from SWISCO at $2.84 each
As mentioned in the earlier post, Shower Solutions has the rollers in stock too. Their price is $4.95 each
I also found the rollers available through Camping World and on eBay but both had prices in the $5-$10 each range.
If anyone knows where to find the other parts such as panels and hinges for the Tub-Master shower door please do tell.
Seems like a good undertaking for Vintage Trailer Supply. It's my understanding these Tub-Master shower doors were used in a variety of RVs as well has residential applications.