If you only want the "correct" base material, have you tried simply using Canvas White or Cream?
It's obviously not correct, but it should give a somewhat similar, "fiber-y" feel. A bit similar to how you can use Rubber colours to create the miky variants of Transparent colours for parts cast in PP/PE like 30093.
It's obviously not correct, but it should give a somewhat similar, "fiber-y" feel. A bit similar to how you can use Rubber colours to create the miky variants of Transparent colours for parts cast in PP/PE like 30093.