You can buy replacement pocket kits from stores that sell fabrics etc. If you can't locate one locally, take one from an old pair of trousers, or you could try making a pocket yourself using fabric similar to the pocket (from old pillow slip, sheet etc.) Cut the pocket shape to double the LENGTH you need (not width) as you will be folding it in half, (so only need to sew 2 sides of the pocket later). Fold it & pin the 2 corners at the open end (the fold will be the bottom of the new pocket). Then put the new pocket over the old pocket so the old pocket is now 'inside' the new one (you can make any necessary adjustments at this point) then pin in place & sew down each side of the new pocket - ensuring you are sewing it to the old one of course. There will be no stitching required anywhere else - but if the open ends that overlap in the middle of the old pocket bother you - just use hem fix tape to close up.
jouk
March 2007