I believe Pittsburgh cases do not use M3 screws (they’re non-metric). Check the specs on their site. They are good about responding to emails too.
I bought screws for a Pittsburgh case a while ago. I have silver and black. I have (I think) 100 of each, minus only a couple, and can send them to you for a very reasonable price. I no longer need them as I went to a different case before using them. Message me if interested.
Kind regards,
John