The rivet nuts came from McMaster-Carr part # 94020A323. Very nice people to deal with!
Washers (#8 polyethylene): McMaster-Carr # 95649A225
Stainless FH #8-32 x ¾ “ bolts (for assembly): McMaster-Carr # 91500A197
Installation bolts are # 8 - 32 Allen with matching grade 8 nuts Buy DOZENS of both--you'll need 'em!