I'm busy working on a sensory quilt for my niece, at the rate the ideas are coming in - it may be rather large! Not to be outdone, my 12 year old niece (sister of the one who is getting the sensory quilt) has been dropping hints that she needs a bag for her DS. I obtained an old pair of her jeans and came up with this, the ribbon, button and strap made from a belt are all recycled:
Editted to add, this bag is now lined with fleece fabric. It was a bit big as I cut it to fit the pocket size. The fleece (taken from a jacket I made my son about 16 years ago) makes the DS fit in more snugly and also provides padding to protect it.