Hey Mate, how did you go in your findings?
I can have any metal made with a 1:1 CNC , most common are yellow and rose gold, 18k solid and real 1:1, correct stampings but more importantly a 100% movement fit.
Obviously aren't cheap, for a Daytona Head, including back plate / bezel / Clasp in solid 18k YG you're looking at about 7500 USD there abouts.
Readily available, just not many people want to spend the $$
Be weary of sellers offering it much cheaper as well, many sellers will CNC them in 10k YG and run 18k stamping on them, so there profit margin is higher, all well and good until someone puts it in an XRF machine and that happy face turns into a big big upside down smile