Great idea! My solution ("Swagman to-go" bottle cage) is similar but requires no tools--just clamps onto the front of the seat rail (the clamp slides to the bottom of cage). Benefit is that you just unclamp it when not needed. Drawback is that it doesn't slide with the seat, so you can't slide the seat all the way forward, but rare that you need to. Sorry I have no pics of it installed (car in storage). Been using it for ~3yr with no fails.
