www.celltei.com - they have fantastic bags - I have a pak-o-pet in black right now, but am having another one custom made for the summer.
I have an xs size bag and Oscar is 2lbs 9oz, he has tons of room in there and tends to curl up into a ball or sit up and look out the top - so my next bag is going to be a petite size. I've looked EVERYWHERE (at least 50 different websites) for bags that are small and compact and don't scream "I'm carrying a dog!". I keep coming back to the celltei though, nothing beats it. (Juicy and Guess have some nice bags too if you don't mind spending the money, I still find their dimensions to be pretty big though).