Unfortunately GS hasn't been heard from since 2009. EBay is your best chance. Nitrotek, in the UK, sells some GS parts. I've bought from them and it was hassle-free. I'd try wanted ads on the classifieds here as well. I wouldn't invest a lot in it though, parts are going to get tougher to find, its already pretty hard to find them now. I have a bunch of spares so I'm probably going to use mine until I run out of part.
I recently found 2 good deals on Associated RC8.2s. These would be a great alternative to investing in your GS. There's a new RC8.3 so the RC8.2 is pretty common and inexpensive to pick up. If you invest in another brand, stick with Associated, Losi, Mugen, Kyosho, or other big names who have been around a long time. It's usually best to choose one that your local hobby shop stocks parts for.
GS made a great product but never established a solid market in the US. They're a small wing of a big Taiwan company called GS Silicones.
Do you know which CL-1 you have? There's a rtr, CL-1, CL-1 Advanced, and CL-1 Advanced Plus. Good luck in your search for parts.