Where can I buy spare screws?

To be compleatly honest with you I have a bin full of random screws and parts from mostly American flyer s gauge, old train parts, and I take a lot of electronics apart. I'm from the 90s / im 35 and I just eye the size of the screws the size in 3 ways how long, the tip comes to a point?, and how much fatter is it from the the original screw and if it looks like it matches those rules your probably very good . And even if u do go a little bigger the worse that could happen it itll tear down the plastic beam the joints the two parts but not all it'll save just enough to hold as good as the original! NO LiE I REPAIR ps1,2,3 and ps4 controllers constantly on a daily basis!