I like Wareyin's custom size idea with no buckle at the back to catch on things or show under a waist coat. But most off the shelf straps are sold by waist size and adjustable within a range. Actual strap length will be longer - how much exactly I don't know as I went the route of using sporran hanger straps off of my belts. Most online retailers have toll free phone numbers just for these kind of questions. Find one you like and give them a call as I suspect "the extra" varies a lot from various merchants.