Chrysler used to sell a repair kit for collapsed shafts.
I have a picture of it around here somewhere.
Pretty sure that it isn't available any more. Probably due to liability concerns.

People have repaired shafts in other ways.

Some people weld them solid, but that defeats the purpose of having a collapsible shaft, so it's not exactly recommended.

I've also heard of someone buying a small plastic bolt (look around the plumbing section of the hardware store) and then drilling and taping the shaft to accept the bolt. Screw it in and grind off the plastic head so that it's like having a new plastic shear pin.

I've even heard of several people who just pull it out to the right length and don't fasten it with anything. They say the tiny roll pin in the coupler will hold it in place. (not all couplers have that pin by the way) Sounds pretty sketchy to me, so I wouldn't recommend trying that.

Tav