YES PLEASE RIVET FOREVERYes, you can cry now.
I think its new crankcase time, just to replace the mounting location for the generator / clutch lever arm as yours was sheered off.
There is a very small chance that someone who is GOOD with tig welding or aluminum work might be able to weld the bits back on or weld in enough material to re tap and dye, but the chances are slim.
JB weld would likely just make a mess and be a waste of time, so id advise against it. ( Not to mention, you kinda NEED the clutch lever arm to be held in place tightly. Last thing you want is it to come loose at 80mph. )
Everyone please use a Rivet link when replacing your chain.
As for new parts welding and what not, I feel welding.is out of the question because the part that broke off that the bolt threads in basically blew apart.