Why is a separate gear not available for blending door actuation System

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Passenger side ac on 2011 Grand Cherokee Overland does not work. Took it to dealer. Gear driving blending door is broken. Dealer says I need to buy a whole assembly for $287.50 They then will remove the gear from the new assembly and replace the broken gear. This is the less costly approach for an estimate of $560. To replace the whole new assembly is estimated at $1200 plus. Does anyone know where I could buy the gear by itself?