The plastic looks like ABS. To be on the safe side, I'd ask ToCAD to confirm that.
ABS is soluble in acetone. Carefully apply acetone to each side of the break, press together, and in about 5 minutes the weld should be stable. This would be stronger than an adhesive bond.
Naturally, you'll approach this at your own risk. Before you repair the lens hood ring, you might want to familiarize yourself with the action of acetone as an ABS welding agent by working with some scrap ABS pieces. Good luck!
-H.