Hi Marty.
I can't answer your question (would like to know myself) but if I remember correctly, Kevin Manley at Kevin's Classic Cars in MN told a few years
back that either he was restoring pop open caps or knew a guy who was. You might try giving him a call.
Kevin Manley
Kevin's Klassic Cars
Mobile: 612-275-8722
Kevinmanley2005@yahoo.com