As Jerry said, make you a bushing. You local parts store should also have bushings in stock for that purpose. Gates makes these and perhaps other brands make them as well.
The parts store I worked in keeps these still due to ill fitting hoses or engine conversion.
Works well, and looks like a factory hose when done.
Here's what they look like.
http://www.amazon.com/GATES-BELTS-HOSES-26390-Reducer/dp/B000CRHKSG
