Before everyone goes crazy with suggestion...a 15A cig socket may be all he needs,
The inverter will still function if he is only drawing 60 or so watts for a laptop or some LED lights. That's why I posted look up the "needs".
As long as it is all protected by the right size fuse for wire and socket.
Lots of us have plugged a 50A boat into a 30A outlet and managed out electric needs.
I will say I very much dislike and mistrust cigarette lighters on boats. I switched to these.