The “Raspberry Pi Zero W” is an updated version of the Raspberry Pi Zero: it is identical to the previous Pi Zero model but now features on-board 802.11 b/g/n wireless and Bluetooth 4.1 LE.
While it lacks some niceties, like Ethernet and full-sized USB-A ports, it’s smaller than the flagship Pi and a fraction of the cost.

The Zero and Zero W use the same BCM2835 single-core chip that was in the original Raspberry Pi, but clocked at a higher speed of 1GHz instead of 700MHz. The Zero W uses a Cypress (formerly Broadcom) wireless chip that’s also used in the Raspberry Pi 3.

You can buy it on ebay.