What is the screw size pre-threaded in the Micro Metal Gearmotor HP? I have the 1:150 and the 1:250 and I'm assuming they are the same size. I was not able to find it anywhere on the specs and the hole is too small for me to accurately measure. I took it to a hardware shop that specializes in screws and they did not have a screw size this small. I am not familiar with screw size nomenclature so I'm mainly just asking if you sell the screws that fit in these motors and if so, which ones are they?