When opening a tin with a tin opener, the beatitude of the tin opener is added to the tin similar to how markers and scrolls work (e.g. a blessed tin opener opening an uncursed tin will treat it like a blessed tin).

Delicatessens buy and sell tin openers, though they may not actually generate with any (it would internally appear on the list of the shop’s wares, but with 0 frequency).

Also, the canned food factory shop type in UnNetHack should buy and sell these.

You need to have hands in order to operate a tinning kit or tin opener.