My secondary battery came with 6 spares, so I've been burning through those.

Edit:

I've tested these screws from Amazon and they perfectly fit the Flex motor protective cover. I decided on torx head screws since they strip the least. You don't have to order those, you just need M4-0.7 x 8mm size, so pick whichever head.

I've also tested M4-.7 x 25mm screws for the battery cover and it was a size off. Looks like M5-.8 x 25mm are the right size. Should know by 8/20.