Power supply help

I have been searching for a nominal 36vdc to nominal 12vdc regulator/supply.

Specifics: I have a 36 volt golf cart and would like to add one headlight (about 10 amps) and a decent car stereo. Yes, its possible to simply tap two of the 6 volt (6 in total) battries but that presents wiring issues and uneven use of the batteries.
Hoping someone can point me to an off the shelf supply or good plans to build it myself

There is a high current, 28 vdc to 13.8 vdc linear regulated supply described in the 1994 ARRL Radio Amateur's Handbook. That might be a good starting point. The challenge - it's a linear supply which means the power transistors waste the difference between 36 volts and 13.8 vdc. That's a lot of heat to manage but it can be done.

I would think that you could power the light with a PWM with a reasonably high frequency - maybe a kHz or two. SMPS would be better but the PWM is easier to construct.

While googling for a convertor for my computer (cigarette lighter in auto to my Dell laptop, 18 vdc) I ran across a company that made commercial inverters in the range you need. All I can recommend is google - I can't recall the name of the company.

Google 48V 13.8v converter or something similar.

As usual, you don't give a clue as to your location. Yes it is important.

I know this is not what you want, but: Put on 3 headlights wired in series. Very simple!