gearbox casing?

hi mate where could i find a new gearbox casing i had mine rebuilt last year after finding out my rear bering hole had become oval eventuly bashing a hole in the gearbox casing
i am a machanic and am very confident i can rebuild it
just want a gearbox to practice with

eventuly i will be supplying a service in my spare time
as we all know that punto gearboxes have a major problem