What engine is on it?
If it is a fairly late model engine, the parts are probably available but I don"t know if the basic engine blocks will accept the starter and/or if the blower housing has clearance inside for a flywheel with a ring gear on it. If it is one of the older flat-head engines, the parts you need may not be available any mower.
It might be more cost-effective to re-power the tiller with a new engine set up for electric start. I know Briggs and Stratton has a model for 12v and another for 110v. AC.
If you go the 12v route, you will need a starter button, a battery, a battery tray, battery cables,and the wiring to hook it all up.
The starter on the 110v.AC unit has a plug that accepts a regular drop cord.