get yourself to the next race meet near you and take some pictures of the home made ones. People use all manner of things - starter motors and big angle grinders are common motors. Should be an easy copy job if you have the tools.
Unfortunately there's no Classic/Historic racing north of Brisbane where starters might be used and I am located 1200km north of Brissy! All the race meetings we do have here in the tropics are late model stuff and we just turn the key and hit the button marked START. None of this barbaric push start caper - too hot here for that!!
I'll be at the Historic Meeting at Morgan Park in September and no doubt I'll get some good ideas re starters there but I was hoping to find something before then.