This is my choice: http://www.genuineinnovations.com/bi...px?prodid=1092
Great product and fantastic customer service. It does need threaded cartridges, but for the two or three times a year I might use it, the cost is no big deal. I also really like having the pump for preloading the tube and in case you run out of CO2. It also comes in a carbon version, but interestingly, the Al one is lighter.