I'd sugest you start with trying to get hold of a kickstartswich... I bought a new one at AmiGBG04 for like 8$ and I'm sure you'll be able to dig up one localy for about the same (at least secondhand).
If you can't find one then try out ReloKick... it's realy simple... if you want to run an old game simply boot up with relokick and after a few seconds it'll reboot you machine into 1.3 (I've put ReloKick on my harddrive and have an if statemen in my startupsequence together with a "mousepress program" that run it automaticly at boot if I hold down left mousebutton).
