Suggestions for speedo resto?

[Captain Fantastic]

Hi everyone,

I'm deep into the restoration of my CA77's speedometer.

I've disassembled the beastie and derustified, oiled, spun, repainted, etc.

The little white gasket rubber that surrounds the glass lens has poof-ified and disintegrated.

I need a solution to aid in my reassembly.

Is there a repop part I need to seek out, or has someone tried a divergent solution and can offer up some advice?

Thanks,

dv