As has been said, they're likely narrow crown 18 guage staples. If you have a compressor, pneumatic narrow crown staplers are available for not much money; often they also can drive 18 gauge finish nails. (Good ones, such as you'd need if you used one all day every day, do of course cost good money; but the $30ish ones work fine for occasional use in my experience.)
There's nothing especially magical about the staples; you could use small nails or screws or whatever seems appropriate to do your repair work just as well. The staples are just quick to install and hold better than nails (so if you use nails, use a few more).