ABS plastic can be welded. But, as this plastic ages it loses some of its make up to evaporation. Melting/fusing such plastic makes it shrink and become more brittle. You will, at least, need to add filler rod, and learn a new welding skill.
A bit easier is superglue, and a bridge patch (at least on one surface side) of nylon tape and epoxy. The tape is applied to a clean surface that has be roughed up or even grooved, so the epoxy can grab on to something when subjected to later stress.
