Not that anyone should do the following, but this is the solution I have ended up using at AirBNBs for the past couple of years now since charging at 120 volts / 12 amps is too slow most of the time and lugging a NEMA 14-50 extension cord is a huge burden due to the weight.
I purchased a 75 foot 10 gauge extension cord from Amazon which was good for 120v/15amp due to the connector being a NEMA 5-15. I promptly cut off the plugs and replaced them with NEMA 6-20s (240v/20amp) which the 10 gauge is easily capable of handling. That bumped my potential wattage through the extension cord from 1,440 watts to 3,600. Now...6-20 receptacles are obviously not common except in hotel rooms (for the A/C/heater), so I made a wide selection of adapters to get from whatever outlet I might find to a 14-50 receptacle. I then use a 14-50 to 6-20 adapter if I need to use the extension cord to get to the car, and then a 6-20 to 14-50 adapter before plugging in the Tesla charger and dialing in the maximum amps that the outlet or extension cord is capable of delivering so nothing gets overloaded.
So instead of charging at 3 MPH, I can now almost always charge at 10-11 MPH which I find is sufficient 95% of the time.