Many offerings from well known suppliers but how come no subzero ratings?
No -10 or -30 bags.
I'm rather surprised.

http://www.trailspace.com/articles/2012/07/24/water-repellent-down-sleeping-bags.html#comment131597

I don't know how the coating works, but I'd guess that either it adds a lot of weight or it reduces the insulation qualities of down.

Saw a couple of bags at REI with it last week. Has the possibility to really be a "game changer".

I'll let others be beta testers for a few years before trying it myself. :-)

Exped Waterbloc Sleeping Bag might be your ticket!

They have 4 bags that have a temp range from 27*F to 11*F.

Send me a DM if you need additional info.

I'm thinking the logic is that if you need it to go that low, you're not ever seeing high temps above freezing, so water would never be encountered. Not sure how natural perspiration plays into that.