May want to see if this would work for your bike/pump style...
I took my pump and mounted it with my bottle cage. I just took the mounting bolts into my local hardware store and they gave me longer bolts with the same thread size. ($.40) ***Thread size is important, it needs to match. Also, another thing to watch is the head of the bolt should be an allen wrench or screwdriver type so you can tighten it on the road if need be.
I lined everything up like I wanted it and marked 2 spots for holes on the pump holder and drilled them. (I suggest making the holes slightly bigger than the bolt diameter so you have room to adjust it all when putting them together.) I put the pump holder on first then the bottle holder on top of that and bolted them both through the same set of holes.
My pump now hangs on the side of my up tube and the bottle rides on top. (I also made sure my foot, pedal, etc... would easily clear the pump before doing any of the above steps.) I was able to keep both of my bottles mounted.
Hope this helps!!
-X.