Have successfully replaced many stock Klacko Cast Aluminum rollers with Delrin/Acetyl alternatives. I am sure to start an argument here, but I do not recommend using UHMW or Nylon....your machinist will also thank you...what you save in material cost...will be spent on labour to deal with the stringers.
Note that you should have some SS axle/compression tubes inside those rollers.....if they are still in good shape, no need to change out. Definitely not recommended to run without them in place. The roller hole should be bored for clearance for this compression axle to run smooth. The roller should be slightly narrow of the compression axle to run freely.
I may have some old/new stock of the anodized aluminum versions if anyone is interested.
For Delrin/Acetyl replacements in USA, I would highly recommend Meri Marine; He will even tailor make your roller match your anchor shank.
https://dreamgreen.org/merimarine Usually runs $85-150 USD per roller depending on qty and size.