How about a Shoulder Saddle? It's just the thing for carrying little kids on your shoulders. This page shows the Shoulder Saddle and a bunch of other goofy inventions.
I could have used one once. Back in high school some relatives were small and I would give them and their friends rides on my shoulders. Unfortunately one of the kids had ringworm on the inside of her thigh, and it rubbed on my neck. Someone asked me how I got ringworm on my neck and I innocently told them. I have some warped friends.