Any hardware store will carry washers and nuts for the threaded rod stock.
I have a large facility with multiple Wall Hung American Standard Madera # 2233401-020 Toilets
The contractors keep removing one or two of the four the mounting bolts
Is that a standard thread size?
Does anyone have a part Number for the bolts and the flat plastic washers
A/S does not list that number and the Maderas they show are all floor mount. A true "wall mount" has four 5/8 threaded rods for support, along with various nuts and washers in a PRECISE arrangement to secure the toilet and protect it from breakage.
Licensed residential and commercial plumber