Voidweaver repairs - Suggestions?

Normally, I'm okay to have a go at repairing any models that get broken, but this one has me stumped.

Basically, during transit, the rear-mounted shuriken cannon of my Voidweaver came off, with the bit that normally slots it into the back still in there. I'm discovering that it's not the easiest thing to repair, given the position and bulk of the gun compared to its mounting point.

For now, my models are unpainted, so it isn't too much of a problem if it doesn't get fixed. But I intend to start painting my (large) collection of models in the new year, hence why I want to try and fix it.

Any suggestions?

Magnetize it to avoid future incidents?