Source Quick Connect kit for hydration bladder tubes (suits Camelbak/Source/Osprey)
$5
Pickup in Hawthorn, but I can probably post it without the plastic packaging in a standard large letter envelope if you want as well - the plastic bubble bit will make it too big to fit in a standard envelope.
This "Quick Connect" kit converts your hydration bladder by adding a flow stopping nozzle and connector to quickly disconnect and reconnect the hose from the bladder. It suits Source/Camelbak/Osprey and maybe other hydration bladders with the same diameter tube.
I use one to convert my Camelbak 2L so I don't have to feed the tube out through the pack everytime I take the bladder out to refill.
Mine is shown in this post: viewtopic.php?f=15&t=19967
I bought spares to use with my other bladders, but in hindsight, my smaller bladder I use when cycling doesn't really need the quick connect - it's a 1L bag, and I don't take it out often enough to warrant the quick connect.