Camelbak uses a right angle spout so if your pack has a sleeve, you probably wont be able to zip it up all the way and it will freeze easily. I have an older camelbak reservoir that has a straight spout that fits, but it will be harder to find an old one. The thermal tube kit uses a straight spout, but it is very leaky and still doesn't fit into the sleeve on my dakine pack.
What you should do is go down to your local outdoor shop (REI, etc) and take your pack with you. Look for reservoirs that use a straight spout. You probably wont be able to take them out of the packaging so just compare the shape to the size of the area where you put the reservoir.
I personally like smaller reservoirs because I like to only fill it 2/3 of the way full and suck the air out, so they seem to distribute the weight better than larger ones with this method