A pool cage is typically an extruded aluminum structure covered in polymer coated fiberglass mesh (commonly called screen, insect screen, or pool and patio screen). This being the case, a pool cage -by it's very nature- cannot leak, because it is not designed to repel water.
Where to find pool enclosure repair depends on where you are currently. A good way to find pool enclosure repair is to go to google and type in near "your zip code", pool enclosure repair.
$20 to $400, just depends.
To fix a leaky PVC joint, you can try tightening the joint, applying PVC primer and cement, or using a repair coupling.
You can find a professional plumber to repair a leaky pipe in your wall by searching online for local plumbing services, asking for recommendations from friends or family, or contacting a plumbing company directly.
You can replace the rubber gasket.
WWW.funrooms.com offers specs and components for pool cages.
This is a machine shop procedure which the head has to come off to accomplish.
Depends on why it is leaking.
You will need to seal it with some sort of waterproof coating that is NON TOXIC.
You can find toilet repair parts for fixing a leaky toilet at hardware stores, home improvement stores, or online retailers that sell plumbing supplies. Look for parts such as flappers, fill valves, flush valves, and gaskets to help repair the leak.
Often it's a rotted pipe or a leaky hose or a leaky water pump. Usually is't best to look at it and see where the coolant is coming out, then repair it.
Hydralic cement?