Apple do still sell snow leopard. As you need it to go to mountain lion.
From Apple.com US If you’re running OS X Leopard and would like to upgrade to OS X Mountain Lion, first you’ll need to upgrade to OS X Snow Leopard. You can purchase OS X Snow Leopard for $19.99 by calling 1-800-MY-APPLE (1-800-638-7753).
Try giving 0800-MY-APPLE a call and asking. or as above try TradeMe