If you want to do the math game, Apple's reported production capacity was 2,000,000 a month ASSUMING all its suppliers are up to speed. Displays are the weak link and certainly with the last generation they had a high rejection rate at first. That 2 million a month capacity needs to feed 3 channels: domestic retail, domestic online and overseas retail/online (assuming they're going to building up inventories fr next week's launch). There are currently upwards of 8,000 domestic retail locations.
So, dividing 2,000,000 by 30, you end up with 66,000 a day being manufactured. Assuming they've depleted whatever inventory they built up for launch, that's 66,000 per day feeding 8,000+ retail stores and online orders (less whatever number are being set aside for the foreign markets).
Add in the 18 flavors they're producing and the likelihood that you're going to find the model you want anytime soon is slim.