Oh Invacare are pretty decent. Pan had something similar to that before he got the amazing Meyra. Yeah, that's not tippy or splashy at all so you can easily hang tons of stuff on it without it affecting the balance.

I have never really managed to get a normal rucksack on a chair without it either breaking or falling off at awkward moments, or swaying in and out and getting all in my way when I'm pushing or banging into Pan's back. ATM we use a messenger bag and it is a fucking pain, but the bag is cool so eh.

I do recall a kid at school used to have an ordinary rucksack with the shoulder straps over the pusher bars no problem but he always self-propelled so I spose it wasn't an issue.