I'm another baggallini fan. I own 5 totes that fit the description. There are many more styles in different sizes and colors that would work. All have a pocket with a zipper at the bottom to go over the handle of a roller bag. Some also have a zipper at the top of the pocket. Depending on the vendor, the name may not be the same as what I have listed.
You can buy them at lots of online vendors as well as at TJ Maxx. Watch for discounts.
Below are mine. The Hobo can work as a purse. The others are a bit big for that, but all can qualify for a personal carry-on item. When I wear them, I wear them cross-body.
Hobo -- I have 2, one in red and one in blue.
Santiago -- Mine is gray.
Kindred -- Mine is pale blue. This may no longer be available. And it is not small like it says on the listing.
Alberta -- Mine is purple.