I bought one from Amazon, let me see if I can link it up. (https://www.amazon.com/dp/B01DON91Q8...roduct_details)

It's reasonably priced and works pretty well. It clamps to the seat rails so I would only recommend using it on alloy rails. It has two mounting positions so you can have it more vertical, or at a little bit of an angle. I have it angled so the cages sit lower and lean back. Even so, I've noticed on occasion I can feel the top of the bottle if I push back on the seat, that is, if I use the taller style bottles.

Since it mounts two cages, I generally carry one water bottle in one cage and in the other, I carry a tool kit like the one in your picture in the original post. For longer rides, I have a regular bottle cage on the seat tube as well.