| As I've mentioned before, I've produced some kits of stainless steel screws and nyloc nuts for the screens, hence doing away with the well-nuts.
U2U me if you're interested.
But if all you want is a handful of "screen-sized" nylon washers, I can let you have some FOC.
I had a bit of trouble sourcing them myself, but managed in the end. Most easily available nylon washers have too large an outside diameter, and show up as a plastic ring around the screw head, which is rather unsightly. | 
Threaded Mode