Our local John Deere dealer keeps a variety of sizes of straight radiator hose, i think they sell it per 100mm increments? They use it in their own workshop and keep enough on hand that they are also able to sell it over the counter.
I would imagine most machinery agencies would keep some range. I'd either make a few phone calls, or drop in and physically see what someone near you has got.
If you need to go around a corner, i have made radiator hoses out of straight hose and steel exhaust tubing bends to get the required shape. It is also an easy way to make a hose that needs different size ends.
