Look at a TICONA material, UHMW-PE, it can work wll at -253
degree celsius. I think this will be cheaper than Teflon, and work better too.
Ståle Eliassen
Fortron, from Ticona, is a PPS, with 0,03 % moisture
absorption limit. Colour might be a problem, there are limited choises for colour, but it should work with your other demands.
Eliassen