In my experience Epoxy won't hold as it's ABS plastic.
I plastic welded mine and then reshaped it, filled it and repainted.
You can add fibreglass as a stiffener but that eventually peels off as well since the resin is just another type of epoxy.
Good tips but afraid its too late for that, used up nearly the entire amount of JB Plastic Bond with strips of Bondo panel patch and clear epoxy'd the turn signal. Seems stiff atm, if it falls apart may just go for a new fiberglass GPz fairing and do this:.
https://imgur.com/a/ARDO79U