Fairly easy teardown … long out of warranty. WVOD1
Battery seems to be labelled - PT124147 - has a 4-wire lead.
No luck looking on amazon or ebay.
Replace with something better that gives you everything without a subscription and no 5 minute cool-down if you don’t 
Argus MagiCam - 2MP Wireless Magnetic Camera with Battery Life of 9 Months [Official] Argus MagiCam - 2MP Wireless Magnetic Camera with Battery Life of 9 Months
Perhaps , and - comes with a pair of AA lithium batteries that are not covered by the warranty.
That’s not their only model, plenty of options…
But up to 9 months on a disposable battery isn’t bad for not using solar…
You have many choices between Tapo & Reolink
Well, upon further teardown (battery) it appears to be 2 3.7v … so to just find the correct closest batteries to match.
Are you able to use a wired camera inside looking out? This Cam v3 is 4.5 years old and the camera, power cord, power brick and SD card are still working.
This is the view of what this camera sees.
I am happy I have not had to mess with replacing a battery. I think it has lasted a long time being out of the elements.
I already have some V2s and V3s doing that. But this Outdoor cam was out of reach for power so I had it on Solar.