There is a socket that has a coarse left hand thread in it that is tapered that can be used to fit over the lock. It just bites into the lock and spins it off.
You can probably get it at a good, local parts store. Someplace like NAPA.
I know what those shops mean, though, by not having the room to do it. I could barely use my stock lug nuts with my Cobra Rs. I bought McGard spline drive lug nuts instead. They work great. When you get the locks off, I recommend you try those for your wheels. Here is the page on the spline drive lug nuts:
http://www.mcgard.com/automotive/new_prod.asp
Our locks are made by McGard (if they are stock). You may want to contact them and see if you can send them an etching of your lock to help them identify what key to use.
http://www.mcgard.com/contact/ is where you can get contact information for McGard.