I found my Walker pouch in the gift store at the Whitney Museum, of all places. They were offering what turn out to be the larger “arm gussets” (3″ x 4″) rather than the 2″ x 4″ “wrist pouches.” Both are rectangular nylon mesh pockets attached to a wide elastic, but the arm gusset is large enough to hold a roll of poop bags, a key and a goodly supply of dog treats.
It’s probably meant to cling to your bicep while you’re running, but I just stick my wrist through it when I need to carry it for any distance — it’s loose but stays on. When I want to dash out with Chloe for a quick bathroom break, I leave my big OllyDog Walker behind and take the Walker arm gusset instead. I keep it in my purse, so that I always have a poop bag roll with me — and the Walker keeps the roll from unrolling into annoying blue plastic spaghetti.