Depending on the formality, why not try the kilts, hose and flashes, a regular dress shirt and tie (plain colour), and maybe a waistcoat or even a sweater vest (plain colour). I wore somthing similar to a whisky tasting last Friday (no tie) and it was a good mix between casual and semi-formal.

This black one would work really well http://www.menswearhouse.com/menswea...=1164143347835 as would this charcoal one http://www.menswearhouse.com/menswea...=1164143347839