1. check the shop where you sold it, usually it takes 2 days in-game for the shop items to get changed.
2. check other shops to see if they sell it, yes it can be found even if it is 1% of chance because sometimes when I go to shops I see it in there.
3.m&b morgh editor, you can edit in-game items and troops' gear with it (not sure if you can increase its chance of appearing in the shop though but give it a try also backup your save files because idk if it mess them up

).