Is there a Nalgene adaptor cap

http://cascadedesigns.com/msr/water-treatment-and-hydration/water-treatment-and-hydration-accessories/3-in-1-cap/product

and this

http://cascadedesigns.com/msr/water-treatment-and-hydration/water-treatment-and-hydration-accessories/hydration-kit/product

could also use this

http://cascadedesigns.com/msr/water-treatment-and-hydration/water-treatment-and-hydration-accessories/spigot-cap/product

and if you like a shower this works well also

http://cascadedesigns.com/msr/water-treatment-and-hydration/water-treatment-and-hydration-accessories/shower-kit/product

I did not know that the MSR stuff fits onto Nalgene. Is that a standard size being used across many products? That is quite wonderful. I think the spigot cap is probably the best usage. Thanks.

SmarTube makes a drinking hose for water bottles and has a 63mm adapted for wide mouth Nalgene bottles.

http://www.bluedesert.co.il/smartube_caps.html

Now, the hard sided Nalgene needs a one-way relief valve to let air into the bottle so you can drink from it. With a soft-sided bottle, you don't need the valve to equalize the pressure, so you could get a "bulkhead" barb fitting and drill a hole in the Nalgene canteen cap to suit.

See http://www.eldonjames.com/html/SpecialtyConn.html#Bulkhead for examples of bulkhead barb fittings in small hose diameters.

Small diameter bulkhead fittings are hard to find and expensive. You could drill a hole in the cap, and put a suitable length of hose through the cap and glue it in place with food grade silicone sealant. DAP Household Adhesive Sealant 100% Silicone is food safe after a 48 hour cure.

I'm tempted to build my own drink tube system for the Nalgene canteens doing just that.

Fits great, no leaks/issues. I swap them around as needed.

REI carries a cap and hose/bit valve to turn you nalgene bottle into a hydration system (I have one). It will work with the semi-hard bottles, you just need to blow air back into the bottle every once in a while.

That cap and hose would work.

Do you have an item number or model name?

I can't find it online. I'll try and look at mine and see. Next time I'm in REI (Sunday at the latest) I'll look if I can't find anything on the one I have.