I wasn't terribly satisfied with some other Nikon Lens Cap Holders out there, so I designed my own using Fusion 360. This print will fit all LC-52 Nikon Lens Caps. It has a slight draft on the inside ring to make sure the lens cap prongs get a good grip.
I've included the STL file and the F3D file if you'd like to make any edits. The F3D timeline has further steps for adding embossed text to the inside bar.