Weird request

[neophyte]

Or perhaps 2 dowels about a foot long. Dip one end of each about 3-4 inches into liquid rubber, drain and let dry. Lay the dowels parallel, wrap a few rubber bands around the undipped ends (cut notches to hold the bands if required). Spread the dowels apart to form an upside-down V, place the open, dipped ends around the door knob, and secure the dowels above and below the knob with more rubber bands. Positioned vertically, the dowels shouldn't cause the knob to turn unless sideways pressure is applied, and less than a 45 degree lean should turn the knob enough to open the door.

Or use mrbigstuff's idea and use your knee to push the lever down.