The best way to repair ABS is with more ABS, but in a pinch fiberglass will work. Acetone will melt down shredded ABS into a paste and you can apply it to the broken section "like spackle" just like George says. There aren't many paints that will stick to Polyethylene, and when it starts to flake off, the machine looks like it's molting. ABS will take paint, but any scratch shows the bright yellow through and doesn't look too cool either. ABS can, with a little work, be brought into a "like new" lustre. If your Attex is a 1976, it's the orange one, and Poly. Good luck.
Stuck in the seventies- not in the swamp.
(6) Attex, a Hustler, a Super Swamp Fox, (2) Tricarts, (3) Tri-sports, a Sno-co trike, 3 Dunecycles, and a Starcraft! ...so far