Thank you for the excellent write up. I'm replacing these bushings on an SM3 and I was also looking for something better than the flat rubber washers, since those are clearly not OEM.

I found a similarly sized rubber bushing at my local Ace Hardware. Interestingly, my local Ace did not carry Hillman, but I found a bushing that had all of the same dimensions except that the ID was 5/32" instead of 3/16".

Thanks again!