Jim, do you want these for use with leather bellows lock straps or for keyboard trim? Would you be using them on one or your pre-WWII accordions? I could make some for you, You could email me directly and we could talk more about it.

Jim,
They're called finishing washers. Available at Lowe's, Ace Hardware, or anyplace that is supplied by the Hillman Group. See link #1 for Lowes #8 brass.

Ned, not the same as finishing washers. The ones Jim is talking about are bigger. I've only seen them from accordion parts suppliers, and only in silver.