Here's an interesting product that I recently heard about: gardening shoes that only cost $9.99. You can check them out at www.nufoot.com.
They are made solely of neoprene so are moisture-resistant, anti-skid and form-fitting. They make a "Mary Jane" shoe in bright colors (hey, making a fashion statement in the garden is always important) and they make a slip-on style.
They seem pretty ingenious to me so you might want to take a look and see what you think. I wasn't able to locate any dealers in the Spokane area but you can order them online.