This subject came up recently in another post so I thought I’d share what I tried. I went to McMaster-Carr and ordered some plastic washers that came in today. They’re a good size match but a little thinner than the originals. I’m thinking they should do just fine keeping the nut from damaging the packing. If they’re too thin I could just use two. I just ordered a bag of the thicker ones and they look like they should be a closer match. With shipping the 1st bag of 100 was $15.42…the thicker ones are a couple bucks cheaper.
https://www.mcmaster.com/#nylon-flat-washers/=1bsrlc3