Go on Amazon or newegg and just look for "m.2 screw kit" and you can get one for a few bucks.
The threading is 2.0 x 3mm CM2x3-3.3. You might find them at a store that sells screws loose like Ace Hardware (if your in the US) but I highly doubt they will have them a big box store such as Homedepot/Lowes (US again)