I don't want to step on anyones toes here but check this out.
www.toolsforworkingwood.com sells 3" x 15" strips of Genuine Horse Butt for $22.95.

He also sells Norton and Naniwa stones, pumice, rottenstone, diamond paste and a fine grade CrOx.

The Horse Butt will make a fine flatbed strop. Good sturdy leather.

Jerry