3D Printed some simple adapters from the Rota Torque center cap size to the Lotus center cap size.
Rota Torque center caps are 62mm across. The Lotus caps have a 50mm ID for the section that attaches to the wheel. The Rotas have a lip about 1.5mm in to hold clips to. The Lotus caps have their clips inset 3mm.
Could use a bit larger "clips" to go into the wheel but I just applied some silicone (better safe than sorry) and they're in there solidly now. The OE caps snap in very strong and I'm not worried about them coming loose.
Wouldn't use these at the track as the ABS would probably warp under the heat, but since the Rotas are my street wheels they're perfect.
Attached the STL file if anyone else with a printer wants to use it - again, I'd probably make the clips a bit bigger if I did it again, but they work.
Oh, and these will only work with the "Tall" OE caps. The "Short" style won't clear the rear axle nut. Some taller adapters could be made but more finish work would be required to make them look good.
Printing:
Before paint:
Painted:
Turned out: