I feel your pain; most of the LHS's around here don't stock GS stuff. A couple do, and they sometimes stock common stuff like suspension arms and gas tanks, so it's not a total loss I guess..
I just keep my eye on ebay and pick up spare parts when I can get them cheap. That way, I'll always have a commonly broken part like a suspension arm available. I don't mind having my own stock of parts, it's very nice actually.
The thing I've noticed about Ofna, is that although a lot of stores carry the parts, there's so many Ofna buggies that it can sometimes be a chore to find the right peice for your particular model. Fortunately, some parts are interchangable, but not all of them.
As long as you can get parts online within a resonable time frame, you should be all set.