One year ago, we did the same search you're doing. There aren't a lot of options without driving a bit.
There are several "condo" options if you want to purchase. Obviously expensive and it depends on what other amenities you want. Will you be storing other equipment or just your Airstream?
We originally rented a spot that was too narrow and too hard to back into. The door width is critical. We could barely open the airstream door when it was parked. Too much anxiety.
My advice - go big- wider especially. The storage unit door is often much narrower than the unit.
It's a bit of a drive for you but Sharp RV Storage in Elk River has wider doors. Heated floors if you want too.