If you are planning on fabricating something your self I'd go look for a piece of sheet nylon. That is what I've seen traditionally used for that purpose.
Delrin will be a bit more resistant to wear. HDPE is available in various grades, and a dizzying selection of shapes. I've purchased lots of different items from McMaster-Carr, they're very easy to work with, have a HUGE inventory and very fast delivery. I've been using them for industrial supplies for a long time, always a good experience.
There's a guide chart on their website for selecting plastics, very helpful.
Starboard, a highly pigmented HDPE, would also be a reasonable material to use. Not as hard as Nylon or Delrin but at least in the boating world maybe more readily available. Certainly easy to fabricate.
But any of them will work.