I recently bought those components:_br_Assembled MK8 extruder and Pro B and Pro W Printer MK8 Extruder Holder but there is something missing? You can't fix the extruder to the holder?_br_I saw on the a photo on the holder page a white metal plate that is fixed to the extruder and which you can use to attach to the holder._br_Where can I get this from?_br_Can you please send me the part number to order it!_br_Thanks.