Hi Bill,
I use an off-the-shelf Celestron Powertank (LiFePO4), which provides both 12V telescope output and 5V USB outputs.
It seems to work fine to power a 12V telescope. My only serious issue is that it automatically switches itself off if you don’t draw some minimum amount of current. My small Star Adventurer mount seemingly doesn’t draw enough power by itself, unless I plug something else into the other USB port.
Best wishes,
Dominic