You can always power it off a huge USB power bank if its a 5 V camera, but if you are not home every day to charge the thing back up then that's no viable solution.
If there is a fuse box in the cabin you could use some sort of way to piggyback on a fuse or unused fuse port there, but that would mean you have some wire to tuck away every day.
Also there might be unused ports for stuff on the dashboard you might be able to tab into, but again that do mean you have to pry off whatever is covering that port.
And you would need some DIY / electrical skills so you don't short things or set fire to your employers truck.
Your employers really should make it so his drivers that actually care and run a dashcam could do so, with their camera they don't just cover their own ass, they also cover his ass.