Only way I know of to shrink leather is to soak it with water then as it dries it will shrink.
'09 Kawasaki Versys ~ '09 BMW 535i
'06 Harley Roadking ~ '95 Suzuki DR350S
'94 Suzuki DR350S ~ '77 Triumph Tiger
'09 Kawi STX15F jet ski ~ '07 Kawi STX12F Jetski
'83 Suzi ALT125 three wheeler ~ '06 Dodge Ram 4X4
'07 Yamaha Superjet ~ '10 Kubota B3300SU