Plasti-Mend is premix ready to go.
If this is a thin weak spot or a flex point the Plasi-Mend website has some sheet ABS for sale. I used some of the thin sheet on a corner and it is holding 10+ years. Can be cut to size with a utility knife and formed around a bend with a heat gun. Get it cleaned & fitted, load both with the goo and prop it into place for an hour+. Touch up and fill any gaps around the edges next day. A bit of an art to apply, and you need to move fast but works beautifully.
Some have reported success with adding some ABS plastic chips to a can of solvent.
