Filters.

These fit in the coax, between the CB and the antenna. The purpose is to eliminate any harmful harmonics coming from the CB. The problem is that this relies on the CB being faulty, as a legal CB should not need more filters.
If the CB is putting out harmonics, then it really should be repaired.

The most common cause of interference to TVs is the TV being unable to ignore signals which it should not be picking up.
The low pass filter is designed to stop CB signals from getting to the TV. The best type of filter to use, is the Braid Breaker type. These cost more than the basic filter, but are more effective.
This filter should be plugged directly into the socket on the back of the TV, not further down the coax. If the person has a video, the filter should go into the back of that, and the lead to the TV should be short as possible.