Did you try use the L2 in Drumheller? There’s supposed to be one there. I didn’t bother, just stayed long enough at Hanna, but Drumheller was my plan B if Hanna didn’t work.
There's apparently 2 different L2 charging areas, but both are in the Downtown(?) Part of drumheller, which is not a quick walk away from the museum. And we were already running very late to a friends that day. So we just went straight thru.
I was actually quite shocked they wouldn't have had some form of charging at the museum... its decently out of the way from everything else. But I did know this prior to visiting.