Remove echo when recording in say, a hallway
The attachment you are looking for is called a lav mic, though sometimes it can be a hand-held shotgun mic, too.  Sound intensity decreases as the square of distance and echoes decay exponentially.  The trick to eliminating the echo is to get the mic sufficiently close to your sound source that the original source is 10dB to 20dB louder than the environmental echo.  If you see how close a news reporter holds a mic up to a subject when interviewing them in the moment (and sometimes in a hallway), do that.

There's nothing you can put on the microphone that will solve the echo problem.  The only way to solve it is with proper distance (which is a function of proper distance ratios).