I really think that if you need a bag for a smaller handheld like the switch the tech pouch while maybe not ideal would suffice.
A bag just large enough for the steam deck and a water bottle seems like a very niche requirement in a world where the tech pouch exists.
I really believe there would be a broader market for a messenger bag that could hold a laptop and maybe a couple other things without being too bulky. Then if you did want it for the steam deck maybe you could carry a few extra accessories like a headset.
Also this would somewhat fill the desire people have had for a smaller backpack.
