The "Glock Tool" is basicall a 3/32" punch on a plastic handle (I believe that's the size), like this:
Lotsa places have it online. Together with maybe a tiny flathead screwdriver and needle-nose pliers, maybe, it is the only thing you will ever need to detail-strip a Glock. It will hold down the firing pin sleeve for slide plate removal (as shown in the video), it will allow you to remove the internals (the 3 pins that hold a Glock together).
An ordinary pin punch from your local hardware store will also do the job!
You may want a small flathead screwdriver handy if you want to pull the trigger assembly out, and a needle-nose pliers for installing springs and such.
Online, you can check:
The Glock Store at www.glockstore.com
Midway USA at www.midwayusa.com
Ebya at (oh, you know that one already, don't you!)
Oh, and for mods and such, search the threads here, you will find a LOT of ideas!