The Dinkum Systems FlareDinkum PRO Screw Mount French Flag Assembly gives you the functionality of a one-flag matte box at a small portion of a matte box's cost. For most uses, one flag is exactly what's required anyhow. The assembly attaches into any 1/4" thread on your camera or rig, and its adjustable arm will find its way, with the flag at its head, to right in front of your lens. The arm features 13 links and is 10 inches long. You can optionally add more links for more length.
You're free to remove the flag and replace it with an optional Dinkum Clamping Top, which will hold various accessories, like microphones, up to 2 inches thick.