Currently, you can't reserve for 9/25 pickup anymore (for most models). How about 9/26? Or any other next day?
This model is currently unavailable for in-store pick-up. Reservations are available starting at 8:00 a.m. on September 26. Please come back then to make a reservation, or shop online now. This is what I've seen on the website
To clarify, I was looking it up for Australia. Odd that the same message doesn't appear for the US site.
Look around and keep refreshing. There's still some random variants of the 6S+ around. I remember last year, I got my AT&T 6+ at the Apple Store on launch day and the next morning, I checked Apple's site and all the local stores had gotten shipments for that Saturday. It's so random. They had all the models in stock.