Missoula, MT to Jasper, AB is 560 miles while Spokane to Jasper is 502 miles. IF renting in your own

My husband and I would like to fly into Calgary, Canada from San Francisco, CA and rent a car to do a road trip from there through Banf, Jasper, Glacier National, Courdelein, Idaho and return the car at the Spokane, Washington airport where we will catch a flight home to SF. I am running into all kinds of trouble trying to find a car rental company that will let me take the car one way across the border unless I pay some exhorbitant fees. Any suggestions on how to handle this car rental problem?
Also, one runs into additional mens travel shoulder bag trouble given some regulations mens travel shoulder bag which restrict renting mens travel shoulder bag a car in another mens travel shoulder bag country and bringing it into one's own country. (this more troublesome on the southern US border than on the northern, but the rules are similar in many cases)
In your situation, Spokane and Calgary are just 400 miles apart, so IN the event you can find anybody who will even let you do it, you could do a one-way rental for a day, drive the whole thing, and then get another vehicle for the rest of the trip - that being a more standard and less expensive rental. (this only works if the high fees are added to the daily rental rate and not in the form of a one-way drop-off fee)
Of the spots you mention Coeur D'Alene seems least enticing, and without it there would be no major need to go to Spokane. Maybe beginning and ending your trip in Montana, with either a same-city pick-up/return, OR a Great Falls-Missoula one-way, would fit what you need?
Missoula, MT to Jasper, mens travel shoulder bag AB is 560 miles while Spokane to Jasper is 502 miles. IF renting in your own country, you would likely find it much easier to be allowed to cross the border with a rental car.