Instead, I used a plastic zipper lock bag. That wasn't very durable, so I started looking for a pencil bag or similar to use. Coincidentally, a notebook computer power adapter that I bought came with a bag, which I converted to a cycling tool kit bag. It has a double zipper, and when unzipped it fully opens, similar to opening a book. Inside the bag there are some mesh pockets that I use to keep the tools separated. The material seems to be vinyl-lined canvas, but I'm not 100% sure. I doubt that it is waterproof, but it is probably water resistant.
The first photo below shows what it looks like when closed. The 2nd photo shows the inside of the bag, and the tools and spares that i pack.
The benefits of the bag are that it is cheaper than a seat bag, looks better than a seat bag, doesn't rub against my legs when I ride, fits in my middle jersey pocket, and provides easier to access to contents than a seat bag. The drawbacks are that it is almost too heavy for a jersey pocket, and it doesn't breathe well, causing me to sweat a little more on my lower back. Weighing these, I'm pleased with my seat bag replacement.
I thought about writing some comments about the contents, but I'll save that for a future post.