Amazon.com: DC 12v Step up to 24v Converter Regulator 5A 120W Power Supply Adapter for Motor Car Truck Vehicle Boat Solar System etc.(Accept DC9-20V Inputs) : Electronics
DCDC-24-12 - DuraComm
Orion-Tr Smart DC-DC Charger Isolated - Victron Energy
Marine DC-DC Converters | 12V, 24V, 36V and 48V DC | 3 - 50 Amps | Newmar | DC Power Onboard