These lined bags have zippers in the bottom. The bags were designed for the bar that extends from the handle bar to the seat, but could be used over the handle bars instead.
This project is sewn, however I am certain a crafter who has had experience using rubber glue could whip this out in a hurry. I know it would have been easier than sewing it. I am sure Velcro would be a great option instead of a zipper, however I believe it would have to be glued. It is not necessary to paint or line them.
I have a friend who depends on his bike to go everywhere. I decided to make him a couple of bags for his bike. This is what I came up with, using supplies I already had on hand.