After quite a hunt and a lot of disappointing results, I finally found the perfect kraft cardstock. It's from Kraft Outlet. If you want something that looks & feels like genuine paper bag (except even better), you want this. Thicker cover weight is the Lunch Bag Kraft at the bottom of this page ($2.75 for 10 sheets). Regular text weight is here ($1.90 for 10 sheets). Both worked great in my inkjet printer.
I'll be sharing the book I am making with this paper by the end of the week.