I took a second look at the OP.

vr, you should have known better than to post here among juveniles...

Look at the Formula One/CART drivers. They have a hole drilled through the centre of the chinpiece of the helmet. Lead a tube from your camelback (or fashion a "docking device" for your bidon) through the hole and close (very close) to your mouth. Works for them in really extreme conditions; may work for you. You may have to experiment with the tubing.

Otherwise, tubing up and under the chin-piece (or over the visor opening) and gaffer/duct taped close to your mouth.

And before some prebuscent person pipes up, I think the invasion of the carbon-fibre-glass of the chin piece with a simply drill hole (and through the lining) won't interfere with the integrity of the helmet's protective factor. I'm not qualified to give this advice, but as with all unqualified advice, that shouldn't worry you.

And, while I know the sorts of challenges vrkelly is facing with this question (as in winter riding), is a full-face helmet the solution or more of a problem?