Hello, I just got this Toshiba RT-80s box but it has a broken handle. The box is not too heavy, not a lot of metal, and I needed some help on any suggestions on what bonding agent would work best to ensure a strong bond that will last. I'm sure crazy glue won't do it.

I would try epoxy. The two part stuff that you mix together. It still might need some sort of re-enforcement. Maybe a strip of metal attached to the inside of the handle so it's not as visible.

Use acrylic solvent. It is thin like alcohol, dispenses with a syringe and melts the plastic. Basically, it chemically welds the two parts.