I recently picked up some "Plast-aid Repair" from Amazon. I used this to close a crack in my overflow and I believe it worked on the white ABS.
There are two parts to it, one is powered plastic along with a solvent. I think the solvent is MEK, so use it outside. (You could also just buy some MEK at a plastic shop and grind up some plastic but the kit is probably easier).
BTW: MEK == MethalEthalKetone nasty stuff, but so is most of our pool chemicals...