The most common type of failure in bladders is a puncture, but we have specific reasons why we don't recommend these be patched. Most punctures are of a 'longitudinal' nature caused by a pinch, and longitudinal cuts in the material of the bladder are very difficult to repair with a patch. The pressure stress of a fully inflated bladder may cause a longitudinal puncture to gradually extend, eventually out from under a patch, and the bladder will again leak. Another issue is commonly available adhesives do not bond well to the surface of the modern bladder materials resulting in patches that do not hold.
Aging bladders often first begin to leak around the elbow or OPV attachment flanges or ultrasonic welds at seams. What has actually happened is the material of the bladder has begun to lose its elasticity as a result of age and/or exposure to UV & Ozone. While the flange could be replaced or the leak patched, similar age related bladder failures are certain to follow.
We don't sell replacement bladders and there is a good reason. Manufacturers frequently make changes to the bladders in wings, and there is no way to be sure that new bladders will be compatible with the existing fabric shell or molded fittings. (This is the circumstance even for our own DGX Gears brand wings.) We recommend that you contact the service department for the manufacturer of your wing and arrange to return the wing to them for repair.