Where to buy material

Hi~ I am looking for some good quality material to make these cargo pants. We checked out JoAnn's and didn't find anything suitable. I am looking both for a shop online or local, I live in the US. Also, what is the type of material you have found success with? I will be making for an 11-year-old boy who wants the pants to look store bought. He is pretty concerned about the material looking like pants he owns. Thanks for any tips.