Careful with that mulitiple bike syndrome it can get out of hand fast then you have to attend meetings and 12 step program to manage the rotation of the rides.
If you were to repair the tourpak I would use some steel as a reinforcing plate on the inside, as another poster said keep it thin but not so thin that it will flex easily, it will need some rigidity to hold everything together.
Mechanical fasteners such as rivets are good but I would search out a good industrial grade epoxy that adheres to both metal and plastic. This should be available at a construction supply that does business to business not to regular household consumers.
Clean all the repair materials with a good quality cleaner/degreaser such as LPS brand electrical contact cleaner. Use enough that the cleaner/degreaser runs off of each piece removing any contamination such as oils or grease. After you have cleaned the pieces "DO NOT TOUCH THEM WITH YOUR BARE HANDS" use new clean rubber/latex/vinyl gloves to handle the repair pieces from then on. The natural oils from your sweat can contaminate the surfaces and lead to adhesion failure
You will need to prep the the surface of the metal to get a "profile" for the adhesive. The profile increases the surface area for the adhesive to bond too. Sandblasting the surface is the ideal way to create the profile, you are looking for 0.003-0.004 profile peak to valley. Grinding is second best but usually the easiest to source tool wise. Use a coarse disc move the grinder fast across the surface in several directions to create the profile, remember you are wanting a rough finish, no smooth.
Surface preparation of the plastic parts is a little more difficult because obviously the plastic is far "softer" than the steel. A coarse grinding disc used at medium speed and moved quickly across the surface will create a good profile on the plastic. If you can cross hatch the pattern on the plastic that will also help with creating the profile.
Have on hand some quick grip type clamps and something to reinforce the plastic on the outside that the clamps will be against. The reinforcing material should be as smooth as possible. Use a few light coats of Pam cooking spray onto the side of the reinforcing material to act as a release agent. Let the spray dry completely between coats. This is so that whatever reinforcing material you use does not adhere to any of the epoxy that might come out of the edges of the repair area.
Use a heat lamp or trouble light to keep the repair area at a constant temperature while the adhesive is curing. Wait the full cure time before removing any clamping or doing any sanding of excess epoxy on the outside of the tourpak.
After the full cure time, prep for filler, primer and paint to match (that short sentence in no way implies the amount of work that those 3 steps entail).