Spring bump stop

Does anyone know where I could find a set of spring bumpers that mount onto a perch (bolted to the underside of frame) just forward of the rear-most front leaf spring hanger? I'm not talking about the over-axle bump stops. I think these may have been part of the heavy-duty suspension package, but not sure. I've tried searching everywhere but so far, have come up dry. Anyone have a clue? Thanks.