The only two NSD options I found available are the LNbits (also available as DIY and heard or read somewhere that Foundation's Passport has or is planning to add that functionality.

There are also other two options for advanced users to convert an old phone or computer into a nostr singing device... but have no extra devices left atm, nor the skills to build it myself!

Before making any decision, I wonder if anyone has found other colder airgapped solutions. Are you happy to share it here below?