I thought this was an interesting question, but no answers so far.
I had a similar rucksack many years ago, and was annoyed when it fell apart. A friend told me I had to get over myself and simply hook the u-lock through one of the arm straps. I’ve been doing that ever since.
It’s kind of uncomfortable at first, but you should be able to find a way to position it where it doesn’t get in your way.
I know this doesn’t answer your question, but it would mean you could choose from a much wider range of bags.