Well, you have to think, it's what, 17, 19 years old? (Released around 1992 iirc) I picked up a new-style SM3k that's much younger than that and the plastic was horribly brittle, so I think that's just the problem here. It was bound to happen at some point, but sadly there isn't a whole lot I can think of to fix it, other than super-awesome-putty-exoxy-hotglue-metal-reinforcement. That, or you could make a new handle out of something like Polycarb. You've already got a hole there to mount the handle into, and with some metal plating reinforcing the places that need to be.
Another idea that just came to mind is installing a large diameter "T" in there with some wide PVC pipe.
I have a question though... how the hell did it severe at the front of the handle? Unless the way you use a bow 'n' arrow escapes me, you'd think it would severe at the back...
EDIT: Actually, all of the above depends on how close the plunger tube rests in comparison to where the hole is. If it's far enough above the hole, then I think a handle replacement wouldn't be that much of an issue. ....But the existing handles do look quite comical and badass.
Edited by Broderick, 19 February 2010 - 08:06 PM.