Most little items like this can be sourced locally.
Try companies that repair automotive instruments, (speedometers, gauges, carburetors, etc...),
aircraft flight instruments, too. A call to few jewelers might also be helpful.
Check with local opticians; inquire which companies repair eyeglass frames for them.
Also, check with clock and watch repair shops, and houses that specialize in fasteners, (nuts & bolts).
If these technicians don't have exactly what you need, I'm sure they can point you in the right direction.