There is no kick starter kit for the YTM.
If all the parts are still in the starter then it's not hard to attach, pull off the starter and see what you have to work with. If anything is missing I would go back to the mechanic and have him replace the parts and hook it up.
The fact that you had it hooked up before is impressive, the vast majority of the YTMs are missing parts for the decompression. None of mine had working auto releases.
1984 Yamaha YT 60 Tri Zinger(current project)
1983 Yamaha YTM 200 (rear suspension kit)..... long term project
2004 BMW R1150R
1972 Honda CT 70
2007 Lifan 110