Found the link http://thecolbertreport.cc.com/videos/509747/smaug
but UK viewers are not allowed to watch it. Tried a few other sites including the suggested comedycentral.co.uk but that also came up with the below message:-
'Sorry but that video is unavailable from your location
It's one of the detriments of living under a monarchy; unless you can give up your silly accents and move to America watch clips from the colbert report at comedy central.co.uk'
However - despite searching it's not there. Guess the Colbert report is banned in the UK (or something equally stupid) or they just want it for US visitors only.
Edit: it's on youtube - for UK visitors use this link https://www.youtube.com/watch?v=gMLd6NIgwtU