Camping with Little Brown Dog!

I use my eBike while camping a lot. I have solar and an inverter but would like a 12 charger for my dj folding step-thru eBike. It would be considerably more efficient to convert 12vdc to 48vdc rather than the solar dc to batteries to inverter and 120vac then through my existing charger back to 48vdc eBike charging.

Sooo, if anyone knows of a dc eBike charger....