There are a number of commercial products available to move bottle cages up or down from the existing braze-ons.
They're marketed as a Bottle Cage Relocator or Bottle Cage Adapter , but essentially they're all a flat piece of metal with holes drilled into it that may have some finishing work to make it look nicer.
Given they're in the $10 range
it's probably a better use of your time to buy one than DIY.
bicycles.stackexchange.com/users/31389/Ephphatha
There are numerous Water Bottle Cage Mount adapters.
I use "Topeak Handlebar Water Bottle Cage Mount" to mount an extra water bottle cage on the fork of my MTB for long rides.
(Nowhere else to put it).
There are two parts: a metal band with holes and a plastic box with a screw to attach and adjust it - there is a screw passing through a metal plate in the plastic box adjusting the height of the plate which effectively makes the adjustment range continuous.
an attachment that goes on a 0 deg or 90 deg and contains the holes for the cage Also Max diameter onto which it can mount is ~38 mm
The offset from mounting surface to cage holes is ~36.5 mm.
Because it attaches with a metal band it is not suitable for a carbon frame.
cost 7 to 9 dollars
bicycles.stackexchange.com/users/18785/Craig  Hicks
I had the same problem of too-low bottle bosses (since I prefer to use short bottles), and could not simply use a clamp-on bracket because the down tube is not round but "streamlined" (yeah, right).
What I did is get a strip of aluminum bar (from a hardware store).
Without going out to the garage to look at it, I'm thinking it's about 1" wide and 1/4" thick, or maybe a little smaller than that.
I cut off a piece of the bar that was twice the distance between the bosses, plus about 2".
I then drilled three holes in the bar, spaced as far apart as the bosses.
(This places the first hole about 1" from one end of the bar, the second in the middle, and the third 1" from the other end.)
To mount, first use a screw through the bottom hole in the bar and into the bottom boss.
Next take your cage and run a screw (you may need to get a longer one) through the bottom hole of the cage, the middle hole of the bar, and into the top boss.
Finally use a screw and nut to secure the top of the cage to the bar, through the top hole.
I've found this to be quite stable --
no problem with rattling, etc (though I suppose it might be a bit rattly for mountain bikers), and it has never bent or come loose.
bicycles.stackexchange.com/users/1584/Daniel R Hicks
You could use one or two of these SKS bottle cage anywhere adapters to move your bottle cage location.
If you used just one, you'd use one of your existing cage bosses.
With two, you have total flexibility in positioning
bicycles.stackexchange.com/users/11160/RoboKaren
If you can't find anything specifically made for this.
Maybe just get a metal bracket or other similar piece of metal.
Hopeful, you can find something with fewer holes than pictured.
Drill some holes in it to customize and place it exactly where you want it.
bicycles.stackexchange.com/users/163/Kibbee
Are there adapters available for moving a bottle cage up/down in the frame? I am trying to move my seat tube's bottle cage down 4-5 centimeters and I prefer using the braze-ons.  Note: the question is about options using the frame's braze-ons, not external adapters.
Adapter for moving bottle cage up/down while using frame's bottle cage braze-ons
bicycles.stackexchange.com
<frames><bottle>
bicycles.stackexchange.com/questions/45557
bicycles.stackexchange.com/users/20002/mkpaa
There are a number of commercial products available to move bottle cages up or down from the existing braze-ons. They're marketed as a  Bottle Cage Relocator  or  Bottle Cage Adapter , but essentially they're all a flat piece of metal with holes drilled into it that may have some finishing work to make it look nicer. A  metal bracket  or other similar piece of metal would do the same job. As they are metal, they are not suitable for a carbon frame. Several commercial bottle cage adaptors are available, which can be used with one of the existing bolts or continuously along the frame. These use metal straps and are therefore unsuitable for carbon frames.
Several commercial bottle cage adaptors are available, which can be used with one of the existing bolts or continuously along the frame. These use metal straps and are therefore unsuitable for carbon frames.