The basic idea for repairing that broken limb is you get thin wire (0.5mm to 1mm depending on need), drill a hole in both sides of the broken piece with a micro drill, super glue both sides together, and you get a strong new connection with the help of the wire. As Garfinkle mentioned, you can also fill the rest of the cavity first before your drill.
Just gotta know what your doing with the glue to make sure you don't spill everywhere, so use a toothpick or something. I had a small spillage of super glue recently on a part and I was able to clean it up with toothpaste polish after it dried a bit.