Don't expect to find a good security camera with cellular built in.
This might be worth looking at:
Ubiquiti | Simplifying IT However I don't know if the service these are designed for comes with a public IP address, so it might be hard to set up remote access.
There are lots of LTE connection options for various routers; the above is just a somewhat simplified platform.
Chances are, you won't get a public IP address with a cellular plan unless you spend a fortune on it. So you would need to set up a VPN server at a location where you do have a public IP address, and set up a VPN client at the site with your camera, and connect to the camera through the VPN tunnel. I've done this several times and it is a real pain in the ass. Not something I can guide a newbie through.
