You'll probably need the model number off the mast. I don't know about Toyota but most mast numbers are stamped into the side of the mast near the bottom.
The problem is, any particular model could have a wide array of mast options. Some of which were converted at the dealer or somewhere down the road by the owner. The mast is almost considered a completely different machine, separate of the forklift.
That being said, the pulley you speak of is probably the same across all models, the dealer is just too stupid to figure it out. The days of real parts men are pretty much long gone. Now, if they can't type model and s/n into a computer and get results, they are lost.