You could likely find something to work at the hardware store. Due to the specific shape of the washer I ended up ordering from Lexus. It is called UZJ120 Quarter window retainer part #6273528040 and the cost was $8.65 plus tax and shipping.
'04 GX 470 my rear side quarter window latch bolt assembly loosened and fell out somewhere. The latch is in great shape but I'm having a tough time finding just the bolt, washer etc to put it back together with the glass. Thanks