Small Lafayette model 99-35081 charger or battery eliminator used for radio or maybe a tape player. Output is 12v DC at 1 or 2 amp. In a nice metal box with toggle switch, LED pilot light and fuse on front panel. Wire up your own cord and plug-in the HT.
Info is here; https://www.radiomuseum.org/r/lafayette_eliminator_99_35081.html