Old school headphones damaged, can someone suggest a good glue?

I have some really old school headphones that I really love, that one of my boys damaged a few days ago - the plastic cracked just about the headphone part. In case you're wondering, I've got one of these:https://www.amazon.co.uk/Lenovo-Analogue-Headset-Sennheiser-semi-open/dp/B000HWVMJO

They're rare as anything now but they're great headphones (before you tell me to run out and simply replace them). Can anyone suggest a good glue for plastics, that isn't too expensive, and will hold them together for a lot longer? I've had them a while but certainly not done with them yet.

Thanks