Perhaps you have seen the TABS canteen straw that lets you drink from a 1 qt, 2 qt, or 5 qt GI canteen:
http://www.genjax.com/browse.cfm/4,3607.html
The PX, General Jackson's, and others sell it for about $15.
I made a few mods to it.
1. Cut off the drinking tube about 1.5" from the top of the cap.
2. Insert a Camelbak filter adapter into the plastic tube
http://www.camelbak.com/government-m...r-adapter.aspx
3. Use a standard Camelbak drinking tube.
http://www.camelbak.com/government-m.../tube-kit.aspx
It will now clip onto your canteen straw via the adapter.
4. Use the Hydro plug to cap the line so it won't spill if you remove the Camelbak drininging tube. Makes filling the 2 qt much eaiser
http://www.camelbak.com/government-m...port-plug.aspx
The PX Clothing Sales store at Ft Bragg had all the Camelbak parts in stock
I use one with q 2qt canteen on the outside of my ALICE pack. I run the tube up through the shoulder starp and I have easy access to the drinking tube.
Drink on the march with your ALICE!