I have a vintage Ciocc steel bike that only has bolts on the downtube and I want to add a second bottle cage. All of the cage mounts I’ve seen online seem to have average reviews and can’t handle the vertical vibration of a seat tube orientation. What are some solutions that people have come up with ? I haven’t really considered the drilling new holes option but could be convinced.
Thanks!
We have an anywhere cage mount through our sister brand, Dawn To Dusk. Called the Bear Hug Mount. Has a super grippy soft base so won’t scratch, silicone coated straps for extra grip. We recommend it when mounting a cage underneath a mountain bike so should definitely work for your seat tube positioning.
Don’t take my word though as I am slightly biased 
At about 3:10 into the video you can see the rider launch off a ramp and the cage stays put :). It is also on Amazon if you wanted to check those reviews as well.
Not as clean looking as drilling new holes, but will certainly do the trick in adding a second bottle cage.