I don't know Regina, but in Winnipeg there were a few parking garages that were heated. If you could find one of those it might help.
The other concern is wind. That increases heat loss. If you can find a sheltered location it would help, particularly one with power for a block heater. It sounds as if you don't need a block heater for your camper to start, so you could use the power for heating/charging. Make sure that it is not one of those power saving ones that cycle.
Have you spoken to any churches where you tune? They may let you park and plug in for a contribution. Having you there may even provide some security for them.