You can machine an arbor to press into the bore. Use larger diameter stock so you will form a shoulder. Keep its length close to bore length and machine along with pulley width reduction.
PS You can wrap the pulley with aluminum sheet to form a shell so the 3 jaw chuck will seat against the same thickness material when bridging the odd tooth location. Have also made aluminum slip rings with a thin slot cut that the chuck jaws can compress onto the pulley teeth equally. Make the bore of this adapter slightly smaller than the pulley ID for a tight fit. Do not use tailstock/drill to open up bore. Get a boring tool for proper concentricity.