Kills me to type it, but think import when looking for a small altermator. Nippondenso makes a small 40A one that was used for an alternator conversion on an OC-4 on the cletrac.org site. You might need to do some machine work as Horatz did to fit a pulley onto the alternator that will fit the belt and make everything run the correct speed. I should be able to do the machine work if you need someone to.
 
[url=http&#58;//www&#46;cletrac&#46;org/newbb/viewtopic&#46;php?f=21&amp;t=2227:3om04cr9]OC-4 article[/url:3om04cr9]