I know they make them. My twins are 10 and I had them. I can't remeber where I bought them, but I'm sure it was online.
It was 2 velcro straps. The strollers have to be the same type. 1 went around the bottom of the stroller near the front wheels and one conected the handles that were next to each other. You could probably make one.
It worked well. It was not as easy to push as my double stroller much it was nice for when we wanted to split up or when it was too crowded to push a double.
Goodluck,
Sandy