Single-tap tower to double-tap...don't want to drill new holes - any suggestions?

I currently have a single-tap 2.5" tower installed atop a black walnut counter. I am thinking about upgrading to a double-tap tower, though they all seem to be 3" diameter. Does anyone have a 2.5" double-tap tower (I googled already without much luck)? My goal here is to upgrade the tower without having to drill different holes in the black walnut. I would like to use the same holes. Any advice would be greatly appreciated!