Tri-Tronics Training Collar

I haven't trained a pup in 10+ years and dug out the old shock collar. It's a Sport Combo G3.
The battery on the collar itself is toast.
I went online and found the replacement batteries to be unavailable/discontinued.
Are there any batteries maybe not specific to the collar but adaptable?
Failing that, I guess it's a new one.
Any recommendations?

https://www.batterycanada.com/tritronics.htm

Just spoke with them and sounds easy-peasy.
Thx!

Also … it is called an electronic training collar …. Not a shock collar …. Don’t feed PETA!