Update to this battery pack -    • Update, and Improved Trail Camera Bat...  
This pack and the update work very well.

This little battery pack has an adjustable output voltage can be adjusted from 4.3v-27v DC with a max current of 2 amps. So it can easily work with any 6v or 12v trail cameras or anything in between. Just be sure to adjust the board's output before connecting your camera otherwise you may damage your camera. I ordered all the parts on AliExpress.com for really cheap but you can order or buy them anywhere. The Protection Board is optional because the primary board includes the recommended protection circuit. The plug is a 5.5x2.1 DC Plug I recommend a 14mm length as the extra length will be nice for some trail cameras however the 9mm is more common an a easy modification to make it work for those cameras. Some of my cameras don't have a DC plug built in. It is very easy to open the camera and attach a female DC plug to the battery connector. I will have to modify a number of my cameras in this way. Be sure any holes you make to keep them at the bottom of the case, and seal the hole once completed the upgrade.

Li-ion Battery Pack Cost
Li-ion battery 18650: $5 (I already had the batteries)
Circuit Board: $0.80
Solar Panel: $1
Case: $1
Protection Board: $0.40
5.5x2.1 DC Plug $0.20
Total: $8

Parts List:
Circuit Board
Search for: Lithium Li-ion 18650 3.7V 4.2V Battery Charger Board DC-DC Step Up Boost Module Integrated Circuits

Solar Panel 5V 1.25W (Recommended)
Search for: Solar Panel 5V 1.25W Portable Mini DIY Module Panel System For Battery Cell Phone Chargers Portable Solar Cell

Solar Panel 6V 1W (Will still work fine)
Search for: Solar Panel 6V 1W Portable Mini DIY Module Panel System For Battery Cell Phone Chargers Portable Solar Cell

5.5x2.1 DC Plug
search for: 5.5x2.1 Plug DC male or Female Cable Wire Connector For 3528 5050 LED Strip Light
or you can make your own DC plug
search for: DC 5.5x2.1 mm 5.5 * 2.1MM Power cable Male Plug Connector Adapter Plastic 14MM

The Case
Search for: Universal Waterproof Anti Fall Black Plastic Storage Box For Flashlight Light Torch Lamp Battery Charger Case Holder

Li-ion Protection Board (optional)
Search for: 1S 5A 3.7V li-ion BMS PCM battery protection board pcm for 18650 lithium ion li battery