Super glue works fine on plastic - most of the time.
Years ago a fellow Pantera owner shared this product. I've had it on-hand for many years now, and highly recommend it. Not really a glue, but perfectly bonds, fully hardens and can be machined.
Durable as heck. I've had an under-water pool sweep fitting repaired with it for 4-6 years now. Still solid.
Not really a glue for two broken pieces, but for building up lost portions, or reinforcement where size is not critical, a great product.