Quote Originally Posted by Bob C.
Ok, I'm going to make a confession.

Ladies' purses often come with a detachable shoulder strap that has clips on both ends. I found that such a strap, from one of my wife's old purses, works perfectly. Obviously, you and the strap need to be the right size to make this work.

Ask your wives if they have old purses, and wouldn't mind parting with the strap. Or, look for one in a thrift store.
One of the sporran straps I received along with the sporran is basically the same thing. It's adjustable so you can use it as either a sporran strap or a shoulder strap.

What is much more uncommon is the simple strap that passes through the back of the sporran and buckles. In fact, many sporrans do not even have the belt option; you have to use clips.