If I go on a dive-trip I always carry an emergency kit with me.
It includes:
O-ring grease
Super glue
Duct tape
Cable ties
Needle nose pliers
Wire cutter
Screwdriver set
Adjustable wrench
Small steel brush
Air gun for connecting to the LP hose adapter
Battery tester
Knife (Swiss army knife or Leatherman tool)
cotton swabs
coin
That all fits in an empty mask box or other small plastic container. If you don’t have space for bringing all that, make sure you have grease, super glue, duct tape and cable ties. You can fix almost everything with that!