I need to buy an Ubuntu phone, where can I buy it? It is unavailable everywhere.
You cannot buy a new retail phone with Ubuntu from anywhere, now. A few months ago, Canonical announced that it is ending development of Unity, and the phone projects.
You may be able to find a used phone on eBay or similar sites, or you may buy certain models of phone, and flash an image from ubports onto the device. Even if you buy an original Ubuntu phone, you will likely need to flash over to a ubports image, to get updates and use an app store.