Hotend adapter for smaller Hotend diameter for extruder body

you can use j-head hotend or bowden hotend from reprap.cc or reprap-fab.org. You don't need to print a new matched extruder parts, just print an adapter.

the extruder body on the picture is suitable for J-head extruder. (Source: http://www.thingiverse.com/thing:18379)