According to what I've read, the size and frequency of shipments to the SBs varies wildly depending on the store. Even in the Tokyo area, smaller stores are only getting 10 or so at a time. When/if the shipments arrive is anyone's guess.
Also, there are rumors that smaller stores outside of metropolitan areas wont be getting anything until late August. You might want to try a bigger electronics shop that carries the iphone (Bic Camera) if there are any in your area.
Your best bet is to find a store out in the middle of the nowhere. If it's in an area with limited demand, you might get lucky. Otherwise, you're probably looking at a hefty wait.