google "ag tires" or "R1 tires", the results will give you manufacture websites, that get into ag and construction tires. once at there sites, do a "dealer" lookup.
R4 tires = industrial tires. but honestly have no idea about crane tires.
as far as phone calling, in the phone book, ya it seems like barking up the wrong tree. due to most of them all handle regular car/truck tires. but if ya keep calling surely someone will have a clue. and quickly give you a name or number.
call places that are a couple hours away from you, prices can range steeply but a couple hundred bucks. and you can find off brand and name brand tire pricing, name brand can be rather costly.
my suggestion, pay for tubes, and have them come out and pull the old tires off and put the new tires on. some places charge by the hour, some per tire, some just for service fee. some may or may not charge for traveling distance.