Can Tow providers mount new tire to wheel ?

Just get a mounted spare and figure it out. And no, normal tow truck drivers don't dismount tires on the side of the road. If you can't figure out how to carry a tire on a rim, and have a flat, be prepared to sit for a while. Or get tire mounting tools, if you're going remote. And they will weigh as much as a rim. Or more.

I can't believe a Transit doesn't come with a spare... That's crazy.

Btw, if you can trust your ladder to climb it, it will hold a little tire and wheel that size.