It is my understanding that in the United Kingdom, it is legal under the Criminal Justice Act 1988 (section 139)and the Offensive Weapons Act 1996 (section 3 and 4) for someone wearing the national costume of Scotland to carry a Sgian Dubh.
Get yourself a kilt!
As an aside, I sometimes carry a Boker boot knife when riding my motorcycle in Florida. It is covered by my bluejeans and Florida CWL.
PS: the bloody English will never forgive us for supporting Bonnie Prince Charlie!