I believe Uvex is the name of the Eastman/Kodak manufactured plastic that the shell is made out of. It stinks and warps when it gets really hot. The dense foam inside is just foam. I think the most affordable bass with the diaphragm pickup is the KK Baby Bass, or possibly one of the other brands.... Corvann, Sendel, Blady.
I am of the opinion that if you really learn the music, it doesn't matter so much what kind of bass you play as long as the note has a strong attack. Electric bass works fine, too. That being said, you can get a great sound out of most electric uprights by doing some kind of muting at the bridge. My preference is the leather mute strap that Steve Azola used to put on his basses to mute the afterlengths. Check out the great bassist Rene Camacho for this sound.