What Kind of Under‐Chair Storage Do You Recommend?
There are several options available, including ones that go under the chair. There’s even ones that are designed specifically for books and other large items. However, because these types of bags are specifically meant for wheelchairs, the amount of off‐the‐shelf choices available is really limited. I think you’ll be much better off trying to solve the issues you’re having with your backpack (or finding a better backpack), than going with an under‐chair pouch, especially if you need something that’s water resistant.
Based on the issues you are having, it sounds like you might be carrying too much in your bag at one time. I would take sometime to look at everything in your bag and decide if there’s anything that you’ve been carrying around unnecessarily. This is important because, even if you decide to go with an under‐chair style bag, having too much weight is going to impact how your chair moves.
I would also look into whether or not you can comfortably wear your bag instead of hanging it off of your chair. Wearing your bag is not only going to give you a lot more stability, but it’s also going to open up more styles of bags that you can wear.
Finally, I would make sure that your current bag isn’t hanging too low and loose on the back. You want as little slack and movement in the straps so that the bag shifts as little as possible when you push. I would also make sure that your front casters aren’t loose and in need of maintenance.