If you can find one for me for a reasonable price, and then find me an onboard smart charger for a reasonable price I'll consider it.
Until then, dc to dc converter.
Seriously, I looked a while back and the prices I found were outrageous. If I were to spend that much, I'd just switch to lithium.
Its really not THAT much on the car that requires the higher voltage. I'm considering the ignition system and headlights. Thats about $25 in parts including connectors that make the headlight converters plug and play.