I think it's fair to say any external charger that accepts usb type-c should work just fine. However, proceed with caution! All chargers are not created equal.
This is what I picked up a little while ago. Works great and even though it's advertised as 3050 mah, I actually received two 3650 mah. Now I truly have two day battery life with my 950.
I just use a couple of thin round hair bands to hold my phone on my wireless portable battery charger pack while I carry on using it. Once the phone is fully charged again I can put the battery pack back on charge.