It's not cost effective to do. You have to replace the flywheel, install a charging system. Make a wiring harness with switch and solenoid. Buy the starter and battery as well. For what it would cost you could buy an engine with electric start already on it.
The part numbers you will need are:
611091 - flywheel
33-712 - starter
33-334 - solenoid
33-386K - key switch
All of these can be ordered from http://www.perr.com/cgi-bin/shopper.cgi?search=action&category=TEC8&keywords=all
or from http://www.jackssmallengines.com/. I contacted Jacks and they do not have the parts in stock, but can order them.
For detailed instructions on how to do the conversion, go to http://www.perr.com/tip18.html
Hope this helps.
Sorry, I did not realize someone had already posted an answer.