I currently use mine with a padded fabric sleeve from etsy, but I've got a Ringo pouch from Shinnorie.com on order that should be here this week. The pouch is mostly to protect it from things like keys, but I did order the one with a pocket so I'd have a better way of keeping my headphones handy as well.
If anyone orders from Shinnorie, email them in advance to make sure they know you're using it with a bumper. They say that since each pouch is custom sewn, they resize their medium pouch slightly to accommodate the extra bulk of the bumper.