I saw a nice double coin model recently: https://www.shapeways.com/product/TEDGZKHRN/d4-double-coin-dice

It's lovely, but not hexagonal enough!

I used a trimmed paperclip for the axle

1) Snip it to a little less than the face-to-face width of the outer hex
2) Add a dab of hot glue to one of the outer holes
3a) Keeping both coins on a flat surface, insert the axle through the holes until it hits the glue
3b) You might need to use a small, pointy tool to push the axle all the way in. It should sit just under the surface of the outer hex
4) Add another dab of hot glue to capture the axle
5) Trim the excess glue with a razor