Look at camera cases. Back when the iPod was all the rage I had the HM-801-sized Creative Zen, I found a Case Logic camera case with a bungee cord hook on top (which leaves total access to the headphone, USB and A/C ports). Right now I have a Crumpler 1 Million Dollar Home, used it once to carry a 4g Touch and a CMOY-type amp in a Hammond chassis, but normally I use my other (larger) camera bags when I bring a whole transportable system to meets (Tamrac Express 6 or Lowepro Slingshot 100 for HD600, two cables, two iPods, Toucan, IEM). I still have the 1MDH just in case I pick up a really serious IEM later that requires an amp, or a really serious player like the HM's or the upcoming DX100. It doesn't have a belt loop but I hate carrying things that way; if it won't fit in my pocket, chances are it's heavy enough I'd rather have a shoulder strap across my torso.