I bought another Marin, but I'm not sure I like Marin bikes. There is something sketchy about them. Seriously, don't buy one because I did, the jury is still out. Don't buy a Chrome bag either. I bought the large messenger style and large backpack on pro deal, but they still cost too much. They are heavy bags, but last a long time.
It sounds like you want to try a single strap bag. Go for it. I have a large Chrome messenger bag. I haven't used it on the bike in years but I use it as carry on when I fly, a couple times a year. It's a useful item that will probably outlive me.