Is the pulley bore viable? If the only problem is the keyway, and since you haven't been flooded with available pulleys, it's worth mentioning again that a new keyway could be cut. My former favorite customer maintenance man (he's retired now) used to have me check the keyway in the gearboxes on his printing presses every year (12-20 gearboxes per press). If they were worn, he would take them off, and have new keyways cut in them. He would go 120 degrees out, so he could get three cuts out of the same 3/4" shaft. If those 3/4" shafts could reliably take 3 keyways, a deck pulley should be able to handle a second.
Another option is to have the keyway welded closed, and have a new keyway cut. All of this requires a machine shop, but isn't that little old irreplaceable tractor worth it?
Hmmmm,The key way in my pulley has become sloppy so I am in the market for a replacement. Please let me know if you have one available. Would ship to 55912,