They don't use leather, they use vinyl, which is soft and stretchy and conforms easily with the shape. Make sure the vinyl is warm then pull off the old cover and cut a piece a little bigger, start by stretching it end to end then pull out and trim the sides using Evo Stik to hold it under the saddle shell. A sharp knife, scissors and a stapler will help as well as some glue remover. You can get the vinyl from automotive trim suppliers like Segal Motor Trim in Manchester who might send you a small piece as a sample. They have a wide range of colours.