The file 'Bottle Cap Insert For Knurled Shaft 3D Printer Model' is (stl) file type, size is 4.3KB.
Another print based around a Source Perrier bottle's cap using Tough Ink from M3D. Although this fits rather snugly against the ridges of the inside of the cap, a little glue won't hurt it. Alternatively, it may just be best to print fairly dense. I went with thick, hollow walls for demonstration purposes and speed, but I would imagine you'd get a much tighter fit if you went for even medium infill. Solid might require a bit of force.
KNURL.stl | 27.4KB |