I sourced mine from a guy in the states. Doug:
skygazer@kennaquhair.com
As far as material properties go Teflon has problems in that it doesn't do well under compression. Hence Delrin being the choice of hypertuning.
HDPE is not a good substitute in this case. It deforms under pressure more easily than Teflon. Delrin (or Acetal) beat both under compression by a factor of 6