Having been in one of those "Get It Done Now" situations, I made a trip to the hardware store and got some 3/4" copper piping. I chose that material because 1) it's cheap, 2) it's soft so it's easy to cut, and 3) it fit over the end of the plug wire boot pretty snugly. Oh, and it's cheap ;) The other main reason I made the tool is because my Dremel hadn't had any use recently and was giving me the "guilt look".
Using the cut off wheel(s), I cut a slot to mimic the crummy plastic VW tool. The long slot is there to give the wire a place to go while you're sliding this widget over the boot. The two "un-tabs" cut into both the short and long slotted sides are for catching the tabs on the sides of the boot's EM shield. Make sure you remove the burrs from the edges, as they WILL cut into the insulation of the wire. Even if you're careful, this can still happen.
To use it, CAREFULLY slide the tool over the plug wire, and down over the boot. To get it over the boot, align the boot's tabs with the slots in the tool. Once the tool it over the boot, rotate the tool slightly counter clockwise to engage the tabs in the "untabs" on the tool. CAREFULLY pull the tool toward you to remove the boot from the spark plug. DO NOT YANK! The small tabs at the end of the tool aren't terribly strong, and will easily bend if you decide to prove your strength on them. If the boot doesn't come off easily, try twisting the tool a bit more to break it loose instead of just pulling harder.
If you choose to make and use this tool, just be aware that you MUST be careful not to damage the wires while using it. It's more of a stop gap than anything, and I really suggest if you do much work on the ignition system, that you get the proper tool.
Another idea I've seen on rec.autos.makers.vw.watercooled is to bend
a stiff wire to go underneath the tabs and pull them up. I think
that's an excellent idea, as it doesn't sound like it would be hazardous
to the insulation on the wire. I haven't tried it, so if you're
interested, go to the Google
archives and look it up.