Well the sitting condition unknown gearbox is a duffer! - No matter/no criticism.

I have tried cleaning it and struggled so I took it to Halifax Clutch N Gearbox.
Well they just called.
The box is stripped and the casing clean but 3rd and 4th gears are shot.
I need 3rd and 4th gears and 3rd and 4th gear hub kit.
Anyone got any ideas where I might get such items?