[mkus]

This part is not available from Toyota it's from a 2006 with dual climate control you can see in the second photo the tab broke off..

 

[JuneBug]

Yeah, this type of breakage is usually caused by some object (Lego, pen, etc.) falling down the defrost vent and jamming the mechanism. You have only 2 options--buy the entire heater box assembly from Toyota or scour the junkyards or Ebay for a used one.

This would be a great use for a 3D printer!!