Rotorbits Landing Gear Foot
Rotorbits are plug and play pieces and connectors sold by HobbyKing in order to make it easy to build quadcopter (and other) frames for flying machines. See http://www.hobbyking.com/hobbyking/store/__1247__501__Multi_Rotors_Parts-RotorBits.html
I'm using a 't' connector with a downward piece as the landing gear for a tricopter but I needed a landing gear foot for it so it isn't just resting on the end of a piece. So I made this up quickly in Tinkercad and uploaded it. You can edit your own at https://www.tinkercad.com/things/8lXcDFktNsz-rotorbits-landing-gear-foot/ if you want.