How can I change the wrist of my new apple watch?

Etsy and a number of other sites have bands that are made to fit the Apple Watch.Just Google "band for apple watch" and look at all the options. Many of them are significantly less expensive than bands from Apple.

I guess that you can buy them on-line or in apple store but you can definitely change them, this is what apple say in their website: A different band can really change the look of Apple Watch. So we created a full range of them in a variety of materials. The grooves in each case are precision engineered and CNC machined to ensure a perfect fit with any band. And beautifully designed buckles and closures provide the perfect finishing touch.
Good luck!