Things that I have in my repair kit for at home and on the road.
A tube of sealant that will stick to a damp surface. You can get it at any hardware store. You don't need the big caulk gun tube size, a small squeeze tube will do for a quick fix. Most often found labeled for sealing gutters and roofs. Buy the clear. It will peel off cleanly later. DO NOT buy one that has silicone in it. Lexell is one brand but there are others.
A bottle of Capt. Tolleys Creeping Crack Cure. This will take care of sealing up those nearly invisible fine crack leaks
that drive you crazy. The ones regular caulking seems to miss. It really works an has solved the persistent leak issues for us on my vintage fiberglass motorhome and on the sailboat. Sometime it has taken a half dozen or more applications to work its way in and build up enough to fill the crack so have patience and just keep after it. Not for wide cracks, just for the nearly invisible ones. Works great when you have a leak at a screw or other fitting, a small gap in a window or door trim or the caulk around them. It's an on a road trip life saver since it is hard to pull and re-bed a window away from home.
Put a small roll of butyl tape in your emergency repair kit as well. You can use it like a wad of chewing gum to plug a small hole in the fiberglass until you can make a proper repair.
A tube of Gorrila Glue Brand Gel Super Glue. It is rubber fortified and shock resistant. It can be used to mend a crack in the fiberglass until you can do the job properly with cloth and resin. It also sticks to metal and many plastics. Also handy to hold the edges of cracks together and aligned to each other when you do that cloth and resin permanent repair.
A stick of epoxy putty. The kind that looks like a tootsie roll with a center and an outer layer. You need it together. If you get a gouge in the fiberglass it makes a terrific filler to bring it up to surface level. The beige color version used for wood works very nicely on fiberglass and is a better color match for most FTVs than the grey colors used to mend metals and such. Auto primer does not stick well to the dried epoxy putty but acrylic household primers do stick to it. After that primer you can top it off with automotive spray paints.
A lightweight, water proofed, ground cloth for a tent. You can purchase them without the tent. It should have grommets in the corners so you can put nylon cord through them and hook it to stakes. This will provide temporary shelter over something such as a broken hatch cover. The size you need depends on your trailer width. Tarps tend to scratch the fiberglass so buy one that has a softer surface. It will come handy as a shade shelter, picnic blanket or for when you might have to crawl underneath your rig or even an emergency two person sized rain poncho.
A roll of 3M Scotch Tough residue free duct tape. Look for the purple label! It is sold at Home Depot, Lowes an at some hardware stores too. Amazing, it really does not leave any sticky residue behind when you pull the tape off. Very handy to clamp things together, temporarily adhere some pieces of Refllectix on the outside of a window when the heat gets unbearable inside while sitting at a campground. Window glass is a heat sink but if you put a covering of Reflectix on the outside of the window the heat just bounces off and never heats up the glass and the interior. It really can be considered an emergency repair if you get stuck somewhere in hot temperatures with no shade or AC.
Guess that means you should have a space blanket or reflectix sheet in your emergency kit as well. Space blankets are not just for getting you warm, they can keep the heat away by using it as a heat deflecting, mini tarp type of shade cloth. I do travel with several space blankets, they don't cost a lot and they are heat reflecting miracles for summer and winter use such as if your heater goes out. Also make a great signalling device to bounce the light
when stretched taunt like a giant mirror.