Rather than spend $280 on replacement vacuum elements for my 300CD, I spent $160 on some shore A60 urethane and a vacuum degassing chamber. Going to 3d print (probably PETG) 2pc molds. The kicker is, the material is only .030" thick. I'm questioning if I can get a leak-free, uniform cast as I have zero experience with elastomer manufacturing.
Hopefully the stuff is here by Thanksgiving so I can socially distance myself in the garage and pour a couple. If it works out well, I've got a couple other parts that could be re-made in a harder urethane plastic.