Are there special pocket hole screws?
Yes, those are special pocket hole screws.  They're basically just self drilling wood screws (which is why they have the fluted tips).  Standard wood screws may work, but you are forced between trying to center a pilot hole at the bottom of your pocket or risk splitting the piece you're screwing into.

As far as finding more of them, just search for "pocket hole screws".  Most of the big box home improvement stores should carry them.



Kreg Pocket Hole Screw with flat head to engage step in drilled hole and thread cutting flute to prevent wood splitting.