ouch - the amount of times I have tried to fix those things - and failed

If it is anywhere on a joint, then it is almost impossible, and invariably that is where they usually are. Should you be lucky and there is some of the plastic wall completely surrounding the hole, then there is a chance you can fix it. You treat it like a bladder puncture and stick a bladder patch on it, or a bit of old bladder cut to size. I have done this where the hole is on the corner/joint too, but it never lasts that long.
Not too much help, I know, but it is a bitch of a problem. Gluck.