The following URL should magically transport you to an extensive
list of equally-magical devices that, if you keep them cool, will
increase or decrease any DC voltage to any other DC voltage with
very little loss.  The generic term is 'dc-dc converter' and from
all reports they're both inexpensive and reliable:

https://www.ebay.com/i/293234996712 
https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2386202.m570.l1311.R4.TR11.TRC1.A0.H1.XDC-DC.TRS0&_nkw=dc-dc+step+up&_sacat=0 

They do their transmogrification by chopping up your input DC into
a maybe 20,000 Hz signal and applying that to a transformer and
assorted other tricks that increase the voltage to whatever you set
on the control board.  Some of them are priced in the $20.00 range,
so they're not a big investment.

There are many tutorials on dc-dc conversion available on-line
as well.

Mark Kinsler