Since rainbow month is almost done (every month is colorful though!), there are still rainbow bags available. These are made from waterproof fabric and have space for most things that don't need a backpack. Size is about 18x24 cm.
Four different ones with rainbow strap: https://ko-fi.com/s/c177a8247d
I also still have the Frankenstein version! That one is made purely from reused things) except the strap. It's created from leather patches and old fabrics for the lining. I have only this one version of it and there won't be another: https://ko-fi.com/s/86a5b8f8f9
If you want to grab any of these and support the stuff I make I'd be really happy.