A vacuum erection device used with constrictor BAND/BANDS (not the rings) should stop any leakage you describe and give him a sufficient erection. See
http://www.firmastore.com/ for a picture of the bands and rings. While I use the injection method most of the time, I also use the vacuum erection device (ved)with a constrictor BAND or two! Note that both rings and bands give out after multiple use just like a normal rubber band does. ( The constrictor bands are basically rubber bands.) They are folded over the ved tube and then slipped off onto the base of the penis once the erection is created by vacuum.