open up the old phone book. to car/truck tires. and just start calling be perared to call 50 plus times. pending on your luck. normally after a few calls will get hits on different local places that handle farm/tractor/industrial size equipment tires. tire size, and who manufactured the tire can cause prices to be any were from double to triple the cost of off brand name manufacture tires out there.
some may charge, by the hour, some may charge for trip, some may not charge a fee at all. i got a better deal with someone a couple hours away, that any one locally a couple years ago. for the 555c TLB (tractor loader backhoe) rear tires.
price can and will vary wildly. all you can do is call directly and hunt the places down near you. to get actual pricing info.
on larger tractor tires, guy that replaced mine, said prefers rim to stay on tractor. so he can use the tractor with a jack under it. to hold the rim in place while using various tools to get old tire on/off. vs just trying to flip flop with a rim.
if they charge by the hour. found that using a recipcating saw, and cutting a few inches away from the bead that touches the rim ( to stay out of the larger wires in the tire) can drastically cut down on labor on how long it takes to remove old tire. just be careful those wires when ya start cutting can come out and nail ya pretty good.