You can buy everything you need to make flashes from the fabric section at Wal*Mart or other department store. Get a yard of the grosgrain fabric ribbon and a packet of 3/4" wide underwear elastic and you'll have enough for sevarl pair. They can be simple or fancy depending on personal preference. You can buy the commercially made ones for $10 or more. And your kiltmaker can make some from wool to match the kilt. I find that the black ribbon goes with just about any color or style of kilt.

Good luck