What engine, internal balance? Have you checked where the pulley actually mounts? Although the ring is wider, i thought most were recessed in that area so a factory spec pulley would still work?
Update: Looking at some that are available i see that some do look thicker. Not sure how high dollar of a balancer your looking to buy. March did have some pulleys at one time that would work on some applications. I believe the Summit balancer will work with the stock pulley if that would be suffecient for your needs.