I have two bags I keep my yarn and supplies in. One is on wheels, lots of space, some nice storage pockets. Got it online at Joann.com The only thing I don't like is it doesn't roll well except very slowly on a very even surface.
The other is a nice shoulder strap bag I got at A C Moores. I like it much better. Plenty of space, nice pocets, and 6 spaces for yarn-in-use with holes at the top for it to feed out of.
Sorry my descriptions aren't too good.