An insight, don't know why it took so long to think of this possible interim '240 volt outlet':
A 12 or 14 gauge extension cord from the far side of the house could be brought over near the 110 volt outlet nearest the car, to make 240 volts available at the custom adapter there.
A 12 or 14 gauge extension cord from the far side of the house could be brought over near the 110 volt outlet nearest the car, to make 240 volts available at the custom adapter there.