Nice job Pete, not sure if this can be of any help, For rivets Ive been using standard jewellers beading tool. It comes in many sizes.
https://www.ebay.ca/itm/23Pc-Handmade-Setting-Beading-Grain-Jewelry-Tool-Diamond-Stone-Beader-Set-Graver/401503836828?epid=9002917188&hash=item5d7b7e5a9c:g:myQAAOSwwvZZOmlA