Wanting to add some custom plugs/sockets/displays to our trailer's C-Line/CBE power outlets, I found a few models for the faceplates themselves and one with a 29mm hole in the middle, but no model of the blanking plate on its own.

So here it is. There are two models - one is a solid lump and one is modelled with a 1.5mm shell. You can do whatever you want with them (physically drill/cut out the shape you want, or edit the design to add your own). It prints fine in PLA and PETG with 15% infill.

Want to edit the design - here it is: https://cad.onshape.com/documents/429351d9c869f1d4dd50228b/w/9f0f8d5a538cc2e1ab0375f9/e/95628635d8b4451fef300207?renderMode=0&uiState=6810d2454b77633d70b68e0d