You can buy a sheet of 1mm delrin 100mm x 100mm for £2.79 on the bay, cut the size you want with scissors/snips.
On a lathe the blade will waste 3mm...
The shipping will probably be another $30, when it gets here 20% vat on the combined part & shipping cost then depending on how it's shipped you may...
As Scrinja says, Krytox.
Inert so doesn't affect O rings like motor oil and doesn't have issues on any metal to metal situations, in fact its slippy...
No Worries and if I find it I'll photograph the form, its probably in my spares somewhere so will likely turn up when I'm looking for something else...