You might be able to find something. From a manufacturer perspective, these are a tough item because unlike wifi, there is no single 3G/4G frequency/carrier. So, you end with a minimum of 2 or 3 SKU's for each camera model. Or, you have to use a chipset that supports multiple carriers, which adds a lot to the cost, relatively speaking. Then you often need to get the unit certified with big carriers to ensure it will operate properly, or else their system won't even allow it to be provisioned on the network.
There are trail cams that have this built in, but I'm not aware of CCTV cams off the top of my head. They might exist, perhaps start with an Alibaba search (if there is not a generic knock-off of it there, it probably doesn't exist :) )
Adding an external router device is probably the easier/faster approach, though potentially less ideal.
Keep in mind too that you're not going to be able to stream much video over wireless broadband connections before running up against issues with data caps or throttling. The typical 5GB data allotment will give you about 96 hours of D1-level streaming per month, or about 3 hours of 1080p-level streaming per month.
A, take a look at Brickcom. They list a number of cameras supporting 4G via a USB port (e.g. this one). I don't know how it works though and what domes they have.
Mainstream IP camera manufacturers almost never support this, so while it might exist, it's going to be rare / niche.
Also from Brickcom, this MD-300Np-C2 is a Mini Dome too.
IPVMU Certified | 01/04/15 11:54pm
Related - Anyone have tried 3G bonding?