Manners make great stocks, but be prepared for a 6-9 month wait, unless you can find what you need in stock somewhere, which is possible. I personally love my EH-1's. Mcmillan make stocks with lightweight fill, but again, a pretty long wait, similar to manners. Can't go wrong with either if you have the patience.
AG composites make great stocks I have heard, and have a much shorter wait time. They may be your best option!
Wildcat composites make some light stocks, they are from Canada, I talked with the owner a bit, seems like a good guy, if you want to save some money, and do some of the finishing yourself, you can get a heck of a deal through them on light stocks.
Stocky's carbon stocks may also be an option, they ship from what they have in stock usually, though you may have to inlet for your bottom metal, I know some of their stocks are offered with M5 bottom metal, not sure of their carbon stocks are. I personally haven't handled a carbon fiber stockys, but I have one of their heavy composites. A buddy of mine has one of their carbons, it had an inletting issue, but they refunded him a large amount, and I think he just finished the inletting himself? At any rate, he seemed pleased with the outcome.
I think there are a couple more options, but for some reason they aren't coming to mind.....
One more option for a light weight long range stock that is a little different.....
XLR makes a magnesium chassis, and can be set up to be as light as 28 oz, lighter or as light as many carbon stocks, but in a chassis. Make it a folder for 4 oz more, would make a slick back country back pack rig.
Hope this helps!