Hmmm, crazy. I just dug through all the fiche over at Riva, same thing. Maybe call up a dealer and see if he can play fetch for you?
I've actually been curious on some alternatives to stock nose foam. We know polystyrene will turn to napalm with gas, and 2 part eventually soaks up water. Maybe pack it full of pool noodles? Those break down eventually, but last long enough.
*EDIT* Also, you might be able to make the nose foam work from a 750 or SXR with a little trimming. Those are still available. Seems like they are about $70 new. Maybe a big chunk from a couch trimmed to fit, if all else fails?