Here at Wight scooter services we have designed and make foot peg extensions for the Vespa GT & GTS range .These extensions have been on the market since Feb 2010 and seem to be quite popular.
They do not replace the existing foot pegs they just slide on to them so no modification needed.
This will include a sleeve that slides onto your foot pegs first, to help protect the finish of them.

Please email for more details.