Hi Argilla,
Here is another source for spikes and other supplies.
http://www.cocry.com/
A good place to do business. I have no connection other than a satisfied customer.
You might want to think twice about using Stainless Steel spikes. Because they don't rust they don't grip in the wood, every time the weather changes they creep up out of the ties. The best for switches is to buy the spikes long enough to bend over on the bottom side of the ties.
Good luck with your project.
Rick