I haven't had much success with anything other than JB Weld(a dark grey 2 part epoxy), and fiberglass reinforced epoxy resin for really badly busted stuff. Duplicating the leather grain finish of our dash parts can me a difficult task, so I try to do all repairs to the backside of the plastic part, with as little glue as possible on the front side. Any repair will probably need painted to hide the crack, which gets into difficulty matching paint colors, but I've had success matching parts with two spray cans of really close colors of tan sprayed simultaneously. I practiced on a lot of beer cans before bombing the parts.
Eastwood sells some plastic repair stuff, which are probably just epoxy resin kits. Might look into their stuff. I've never tried it, but I do have some of their other products, and their catalog is good "readin room" material.