If your not concerned about correctness, then I'd suggest an alternator. They are cheap, plentiful and if you take trips, can be found even in the smallest town.
I know that some people sell conversion brackets, but they are easy to make. I am the last person you would want to fabricate something for you, but I converted my 59 cadillac in about an hour, including wiring. Lots more charging output, stronger battery, brighter lights, etc.
my 2 cents.
