I've sourced dials from any place I could find them. Otto Frei has blank dials that will fit ETA movements, painted but easily sanded down to bare brass. Those with date windows are in the ETA position, so they will not line up correctly with the date magnifier on a Rolex crystal.
The cartel Explorer II can be used to build a 6542 by grinding the crown guards off, or as a 1675 with reshaping the guards. I used the dial that came with the watch and the movement, again sanding the dial to bare brass.
I bought a genuine Rolex Submariner dial on Ebay that was really trashed, and sand that down to bare, soldered on dial feet to fit ETA.
And I've taken bare brass sheet from a hobby store, rough cut a circle, drill the center hole and used a bamboo shish-ka-bob skewer as an axle to spin the dial on a bench grinder to round and size. Using metal, like a drill bit, makes the center hole bigger and ruins it. Then attached dial feet for a DG movement.
Most of my work was with building the 6542. I had a gen dial from a friend of a friend, good price, in my first build. The problem is that Rolex used a 'capped' dial to fit it to their movement. That made for a lot of modifying to fit it to the ETA movement I was using. Eventually, several builds and re-builds later, it was flattened front and back, dial feet and decaled, and is in my ETA 6542.