I made it out of a 30 cal ammo can and a small SLA battery that came out of an old retired APC battery backup unit. Like a super budget goal zero type device.
I also added a solar charge controller so I could charge it via solar if I wanted to.
The ports are connections for:
Power Output
Solar Input
USB Power Outlets (phone and USB accessory charging)
These accessory ports are available all over amazon and ebay in various types like a cig lighter jack if that's what you want. I went with an Anderson connector because I use them for A LOT of other stuff.