Does anyone know anywhere I could get a pair of replacement pickup rings for a Les Paul-style guitar, in solid unplated brass?

The closest I have found is this, but they only do plated rings (gold, chrome or black):

The dimensions are:
Space between centres of screws holding ring to body: 80mm x 36mm
Neck ring height: 3mm to 5mm
Bridge ring height: 8mm to 10mm

The top of the guitar is slightly curved (radius approx 16 inches), so the rings either need to be flexible enough to bend (unlikely I think if they are made of solid brass), or have curved bottoms to match.