I am looking for a pattern for a bag to hang on the back of my mom's wheelchair to hold her oxygen tank. She doesn't need the bag at home but when we take her out she has to do a portable tank that just never stays hanging over the handles on the chair. It's dragging on the wheels or it's slipping down the back of the chair and trying to drag on the floor if we aren't holding on to the strap. I've been thinking about making her one that is also a liner for the chair so the weight of the tank doesn't drag the bag down...her weight in the seat of the chair will help hold it in place but haven't figured it out yet. Thought maybe some of you had seen such a project somewhere or that you've made one that you would be willing to share the pattern. I've re-invented many wheels but I'm older now and not as creative as I used to be. Thanks for any help you can offer.