Where is the best place to buy a z1u in the USA?

B&H. Period.

Hi Frank and welcome to DVinfo. The only vendors we recommend here are our trusted sponsors. When you buy from them you help support our site, but you also get the best in the business: http://www.dvinfo.net/sponsors/

Several of these sponsors sell the Z1. FWIW, I also got mine from B&H. If you have the time, go there in person. It's an amazing store and is well worth the trip!