Maybe consider making up a list of all the RV salvage yards you might have the occasion to pass during your travels. Than visit or call them and try to make a deal on a used system. They do make electric jacks for Class A rigs that require the same installation effort those wind up and down scissor jacks do. But they work with much less effort.
If that doesn't work for you, try this:
Scissor Jack 2.5 tonI've heard that some installed them upside down so the 'foot' of the jack is attached to the RV frame, and a custom made round concave steel plate welded to the scissor jack contacts the ground.
Problem with any scissor jack is having to crank them up and down...a chore. So most buy an electric battery operated 1/2" drill and set it up to do the work. It gets attached to an extension rod, as you're aware. More stuff to store and care for.
Scissor jacks would not support the weight of a RV to change tires, but they will add stability so you won't have rocking. I've seen it done on a Class A but don't know how it worked for them long term. They were happy with them though at the time.