I found this tutorial for a handlebar bag. I have a small stash of oilcloth (thanks to a bargain bin in a shop in Fredericksburg, Texas; now I wish I'd stocked up more!). I have a sewing machine and somewhat rudimentary skills, and I have a tub of random buttons and a Ziplock bag of random ribbons. I put them all together, and this was the result:
I took some liberties with the instructions, and I fudged here and there due to the lack of convenient craft-supply stores in our area. Definitely some of these moments:
I made the bag longer than the instructions indicated (and would have been happy if it were even longer and wider, but for my needs it will do). I had to use ribbon for the edging, which gives a bohemian look I like, but was fussy and uneven to work with. With no little girls in our house I didn't have cute colored hair elastics to loop the two buttons together... but we do have a significant collection of rainbow loom bands, including pink ones that never see the light of day. And it could be a long while before I have a chance to shop for hook-and-loop tape, but we had a bundle of mismatched Velcro electrical cord ties that were the perfect width and length to attach the bag to the bike.
My next project will a phone sleeve so I can toss both my phone and my keys into this bag together!