Replacement Power Cord - Dragonfly 7 Pro

I plan to use the GPS / mapping feature of my Dragonfly 7 Pro this winter for ice fishing. I'm in need of a power-only cord that I can put an accessory (automotive lighter socket) plug on so I can run the unit in my truck.

Anyone know where I can find such a thing? I find just this accessory on the Raymarine website but it's for the Dragonfly 5 model only.

Thanks in advance.