Can I use a portable power supply to charge while in the field?

Yes you can. There is a large variety of portable power supplies and external battery packs on the market today.  The allow you to charge it’s battery before you leave on your hunt, then allows for you to charge your Tactacam using the included charging cord.  Of course larger will be better so try finding one with a large charging time and you will see better results.  A power bank or external battery charger with at least a 10,000-15,000 mAh battery will work great. https://youtu.be/iBi3rOHRlvo