Looks identical to my '18 and '19 MXR plugs for the Alta stand-alone chargers. If it were my bike, I'd carefully inspect the underside of the charging plug and it's connections (pics would be great, I could compare it with mine), and if OK I'd then offer money to anyone willing to sell or lend their standard (
not fast) Alta charger and try charging it up. With the bike fully charged/balanced, I think a lot more people would be interested.
Perhaps someone here can confirm the Alta standard charger is an Elcon PFC 2500 / TC-619B CAN model, with an Alta-specific? output cable to fit your plug.
EV Source apparently carries them with "free custom programming" included, they might be able to source & install the cable and plug too.