I'm picking up Lofi's NB in March with the K1s, and I have 3D Printed center caps before. Finding the right material is tricky, I don't have a printer that can do ABS, so lots of the PLA materials dont have the heat capacity or sun loading durability to be used as center caps. Guess that gives me an excuse to upgrade my printer and do some ABS K1 cap runs for GRM folks, and of course share the STL file so people with printers can print their own.
If theyre 3D printed, its easy to emboss a logo on the cap, so no need for fancy cap covers. See these caps that we designed with the Eagle logo built-in, we can do something similar for a Kosei or Mazda logo.