While my main focus is technical goods and apparel I do have a soft spot for heritage goods, including one of the cornerstones of the heritage world; the tote bag.
Most totes have a fixed strap length, and the user must choose between long handles (such as can be worn over the shoulder) or short handles (so you can carry it at your side without it dragging on the ground). There are a few examples of adjustable straps on tote bags, the best example that comes to my mind being the Duluth Pack Market Tote:
Four roller buckles is perhaps the most logical way to have adjustable leather handles but I wasn't sold on it. Unfortunately before I could think of a better system I happened across the Tanner Goods Everyday Tote: