Here is another inexpensive one that looks nice. I like the top load type. Mine has a top flap, so if you get too much stuff in it you can leave it open....or use a large zipper top nylon grocery bags like I got just to drop in to the pannier opening...with the top 4" sticking out.
I found that putting much heavy stuff in the milk crate (like I did in the photos) creates a real top heavy handling situation....like it tries to pull you over on turns. So I put the heavy stuff in the panniers and the lighter stuff...like veggies and eggs and maybe 1 12-pack in the crate (2 if I have nothing else).
https://www.ebay.com/itm/1-Pair-Motorcycle-Scooter-Pannier-Saddlebag-Luggage-Storage-Bag-with-Rain-Cover/283704425334?hash=item420e19fb76:g:g-0AAOSwBTld7cfJ