I have had good luck with the cheap handlebar bags on amazon or eBay. Usually $10-15

they attach with a Velcro strap, so can be spaced for hands gripping the top of the bar.

I tie a shoelace or web strap between the drops, just below the brake handles to act as a support to keep it from swinging down

only issue I had is the zippers are delicate, but not a lot of risk spending $10 or so to try it out.