the only reference i've seen to the possibility of a new clutch sleeve for a toro was in a thread on AULRO two or three years ago where a chap was talking about getting a batch manufactured, i don't think anything came of it though as i don't remember seeing any further updates
i would advertise/ask on every landy forum you can find a couple of times a year in the hope that someone has a gearbox laying about with a clutch sleeve still attached