I actually bought the Jordana Paige knitting purse, and I love it, but I do think it is a bit expensive. I actually knit myself a knitting bag! I made a bigger version of the Fulled Lopi Tote from Hello Yarn http://www.helloyarn.com/lopitote.htm
and I put a pocket inside. Its an easy pattern and all I really did to make it bigger was use a bulkier weight yarn and knit 2 strands of it at the same time. I'm using it to carry around a baby blanked that I'm working on right now.