As far as I know any spreader for that class will fit. Tell the farm implement dealer what you own and he will outfit you. I've got 2 - MF135's and any of the small-medium (not garden tractor) implements have fitted. Some have actually put too much load on the tractor as the same hookup fits some of the larger tractors.
Arear mounted spinner spreader 3ph should cost about $350 at TSC , mine did , holds about 250 lbs of material, I assume it does that's the model #, I guess that's what it means. I use it for seeding lawns, both for seed and for fertilizer, be sure and get the operators manual because it gives you the settings for application.