I picked up a used 2006 Silver that came with a plain straight extension on the comfort handlepost with an ahead stem, and it handles very much like a full sized bike. The ability to use whatever stem you want allows for a greater degree af cockpit adjustment. I seem to remember seeing the plain extension listed as an accessory but not sure about availability.
Also installed an Avid Magnesium V brake set that I had laying about and there are no clearance problems with either functionality or wheel removal.