I have a small bag from Detours (www.detours.us) that measures 8x4x6" and includes a small map holder. I think they have a bag that's even smaller than that, but I needed one big enough to hold my jacket and tights on an organized ride last spring. I got mine from Terry, and I'm pretty sure they sell the smallest one also. I have a WSD bike with extremely narrow bars, and it worked great!