https://surlybikes.com/parts/monkey_nuts
V2 might just be what we need. Yours look so much more artisanal though...
It is because it is 😉
Should be pretty easy to replicate with some brass plate, some square alu stock, a hacksaw, drill and some files.
@Lolo started
London Fixed Gear and Single-Speed is a community of fixed gear and single-speed cyclists.
Lolo
Hulsroy
MisterMikkel
https://surlybikes.com/parts/monkey_nuts