I've seen lots of shopping bags on Etsy as well. You just need to search the supply section. They're sold in smaller lots which makes them very affordable and you can get cute colors.
I started my mega-craft-a-thon this evening. lol We have Hurricane Earl blowing through in the next twelve hours, so I'm all bunkered down and going to spend the day working on craft fair stuff. I created a spreadsheet of the items I'm hoping to have and keeping track of what I've made in that spreadsheet. It really helps me to see my progress. Also, I have a column for how much I'm charging for that item and I can see my total possible profits climb each time I make something, which is good for motivation.