Why not buy a stick on valve from eBay.
ozone or Naish Boston will be perfect.
$30 delivered.
worked a treat for me in the past.
Google a few vids if your not sure.
If leak coming from the screw bit and not bladder, take out black o ring and clean then reverse it.
This solved a slow leak for me.
Hope this helps.

I dont think it will be that much.... I just bought a 8m Ozone bladder and it was only $100 plus $12 postage. After breaking my own rule I pissed around with it for hours trying to fix the leaks, but only when I admitted defeat and ponied up for a new bladder did I get a solid absolutely leak free leading edge. It is amazing how much better the kite flew and my session was just from having zero deflation.

snalberski said..
I dont think it will be that much.... I just bought a 8m Ozone bladder and it was only $100 plus $12 postage. After breaking my own rule I pissed around with it for hours trying to fix the leaks, but only when I admitted defeat and ponied up for a new bladder did I get a solid absolutely leak free leading edge. It is amazing how much better the kite flew and my session was just from having zero deflation.

If you want a spare there is a 2012 ozone cat 8 meter bladder brand new on eBay for $40.
Gotta love eBay.

Fantastic Steve ,and that's why I only fly Ozone

Probably the best example for all the other bullsheet threads as to why you'd support shops