Just remembered the SpareOne Emergency Phone. Seems was not a commercial success, and no longer in production.
Was a phone powered by an AA battery, so with some lithium AA primary batteries could store it for years with no problem.
Edit: Just looked on ebay out of curiosity,
https://www.ebay.com/sch/i.html?&_nkw=spareone+phoneGoing for <$10 each delivered.