Barkertown Sutlers makes such a waistcoat. Perhaps the the designer would be willing to sell the pattern. On the webby, look under "Highland Clothing" rather than "Waistcoats" as the Highland waistcoats are cut shorter to accommodate the kilt. If I remember correctly the clothing designer's name is Missy.

http://www.barkertownsutlers.com/Hom...2/Default.aspx