if you go this route, there is probably a better epoxy out there. maybe something that is fibreglass reinforced.
I would use regular epoxy adhesive and fibreglass weave. Or use epoxy and aluminium rods.
Epoxy and metal rods should be available in a bigger hardware store, or builder's supply store. Epoxy and fibreglass weave is most often found in stores for boat or car repair. You won't need cans of epoxy - a small regular pack of with a pair of tubes of epoxy should go a long way. There should be small packs of fibreglass available for small repairs.
First roughen the inside surface with some coarse sandpaper and clean away the dust - the roughening helps adhesion. Then mask off with masking tape outside where you are going to lay the epoxy.
For the next step, I would recommend thin disposable gloves, popsicle sticks and something that can be wetted with water and used to wipe off excess with: a rag, cotton wipes or similar.
To lay the fibreglass: Cut the pieces of weave to size. You would want several for each piece. Be careful not to warp them too much because they are really flimsy and that happens easily.
Brush a thin layer of epoxy with a disposable brush. Lay down fibreglass carefully, then push it down with the brush and more epoxy. Then next layer, and so on. Be sure to not create any lumps - it is really easy to do so by mistake. It can be frustrating work.
If you get some epoxy where you don't want it, wipe it off with the wet rag. If you get epoxy on the masking tape, it is easiest to tear that off when the epoxy has cured a little bit but before it has become hard.
I would stay away from rubber compounds, polyester resin ("fibreglass resin") and auto body filled - they don't adhere well to plastic.