Try calling the Y-3 store in Soho NYC. I just picked up a pair of 9.5s on Saturday. You might luck out and they'll have one in stock. I'm pretty sure they do phone orders.
7.5 was never an option, http://www.saksfifthavenue.com/main/ProductDetail.jsp?PRODUCT%3C%3Eprd_id=845524446799231&R=888591328006&P_name=Y-3&sid=14BEEF64A5B0&Ntt=qasa&N=0&bmUID=kLFxzzw
Sorry my dude. I'll keep on the look out for them.
If I were you I would demand that they fulfill your order. Tell them you know that other stores are getting them so it shouldn't be a problem for them to take a single pair out of their other allotments to send to you. Throw a big fit.