We include #3-28 x 1 1/2" phillips head mounting screws with Seymour Duncan P90 Soapbar pickups.
We include $4 x 1/2" phillips head mounting screws with Seymour Duncan Dog Ear P90 models.
We do not sell replacement P90 mounting screws at this time, but they should be available at you favorite aftermarket guitar parts supplier.
For further assistance, please contact support@seymourduncan.com