Best glue I have ever used for leather - You can buy it at any hardware store, and even wal mart. Comes in a few ounce jar, pint, quart or gallon containers. Spray glue works for a lot of applications, and its a lot easier and cleaner to apply than contact cement. However, whenever I do something with a big fold or I dont want leather edges to separate, I use contact cement.
http://www.homedepot.com/p/DAP-1-gal-Weldwood-Original-Contact-Cement-207534/203661572