Loftywinds said..
If worst comes to the worst, do it from scratch.
I've re-built a LE bladder from scratch (thanks to Kitepower tips and advice) once and it was not that hard. You just have to be patient and careful, as mistakes are almost impossible to redo or fix.
Most commercial bladders come in various sizes and you'll be able to find the right one that's closest to the length and width of your bladder.
Take your LE bladder completely out to be sure. There are a few videos on how to do this. Having the LE on the ground flat will allow you to measure it properly and purchase the right sized bladder. Kitepower sell Tuff bladders which are 30% stronger than conventional bladders.
Lay the new bladder next to the old one and with a felt pen mark the spots where the valves go.
Purchase the amount of stick-on valves you require including the pump and dump valves (if needed). You may be able to re-use the old pump valve from your old LE bladder by steaming the valve area with a kettle and pulling it apart gently.
Next, cut out the holes. Be careful not to cut over to the other side! A trick I use is to separate both sides of the LE bladder by making a very tiny incision on one of the valve spots and blowing air into it using your pump. This will separate the bladder apart and allow you to cut the holes. The holes themselves is best done with a 20cent coin and a sharp stanley knife. But make sure you've slipped a piece of perspex or some hard surface to cut the bladder on, otherwise you'll cut across to the other side.
Once all the holes are done, again lay the bladder flat next to the old one and start placing your stick on valves one by one, making sure the nozels all point the same say as the originals. Note that the common stick-on valve replacements have a different diameter seat than the original Cabrinha valves. If that's the case you're going to have to come up with a technique to cut out some plastic material to slip over the valve and place inside the canopy of the LE of the kite to compensate any gaps. Any gaps that show up once you've put the bladder back in need to be sealed otherwise you could easily pop the LE bladder.
The rest is a matter of inserting the bladder into the kite as shown on numerous videos and gently pumping her up.
Test for possible leaks by soaking all of the leading edge with a bottle of soapy water.
Good luck!
I found the Lofty digging up some old threads!