If the hole is on the back I think I would just use thin doweling sharpened on both ends. Put in the ground and set decoy on top with tip going through the hole. Think of a circus guy balancing a tray on a stick. You might need to modify the hole a bit. I think if done right you would get some nice movement with a breeze. Or....that might not work at all but worth a shot

Might need to play with the doweling size, location of the hole and what not. Sounds like a fun "Problem" to try some different ideas with.
Let us know what you come up with...post pictures if possible.
Good luck,
BD1