Why use a top tube bag for a child's bike?
As parents, we want our children to enjoy their cycling experience. We had been searching for a way to enhance that experience for our child by finding a way for them to be able to carry their stuff on their own bike. I looked around for a couple of bags and had found an old bag that we had used before. It was beneficial because it allowed our child to carry their own snacks, band-aids, and other things deemed to them to be essential. It also freed us from having to carry the various sticks, leaves, rocks, toys, and other small things that children often collect and carry.
The top tube bag location is great. It allows a child to easily access their stuff, even while riding.
The top tube bag we chose for our child's bike
Our bag was was fine, but there was one problem: everything got gross and soggy when it rained. Napkins, papers, band-aids, and dirt became a wet and mushy commingled blob. So, we upgraded to a waterproof bag a few months ago. We found this bike bag by interestingly-named brand "Clothink":
It was a little bigger than our old bag, but it still fits on a children's bike frame (20" wheels in our case) and is easy for the child to open and close. It looks nice also. It's made from a waterproof fabric. It hasn't rained in a while, so we haven't been able to test out that aspect. It's been great for helping our child store their essentials while riding.
It attaches via a few velcro straps onto the head tube beneath the stem, and the top tube. Installation was not difficult. Also, unlike our previous bag, this one is a little stiffer and stays upright better. Our older top tube bag was a little floppy and often sagged to the side. Functionally that wasn't a big problem for the bike bag, but it didn't look very good.
There are definitely nicer bike bags for children's bikes out there, but they cost more. It was hard to justify spending much more than $20 on a bag for a bike that still gets well-used and tested to its limits by our child. As with our children's' bike lights, we decided to go with a more affordable option as a result.