Forget buying new parts,would probably be cheaper to buy a new zx10

.There is way to many parts you will need ie;gears,bears,dogs,shafts,circlips and im sure i have missed a few to.
The longer you have ridden it the more parts will be damaged.The problem is the gears only engage on the ends of the dogs and after awhile they round off putting more load onto the shift forks and then they bend. Within no time the whole box is stuffed depending how hard you ride.
The mainshaft will not fit from a later model but the one in you bike will be fine they are not normally a problem and all new parts will fit on it.
Another word of advice, if you ride it be very very carefull as the gearbox can jam(like mine did) locking the back wheel. Not a nice thing mid corner!(like mine did causing the need for fairing repairs as well.)
Stu