I don't see how you can do it without spending money. If you just suspend it from the handlebars it will flop around. You need either a rack to support it underneath or something like this to attach it to the handlebars:
https://www.amazon.com/KLICKfix-Hand...3REWJ9YHE3MM1Q
I think it should open towards you when you're on the bike, so I'd remove that outside pocket and attach the Klickfix there. I have no experience with Klickfixes so I can't comment on how well it works.