You can buy them on Adafruit in the form of a device with battery, display and camera (but no wifi). Modules can be bought from Seeed or other usual Chinese places. No "bulk", you can even buy a single module. This, IMO, is one of the most exciting things I have seen in the embedded hardware space in years. At least all that Bitcoin money ended up producing something of value (the company that makes the chip stated out manufacturing bitcoin mining ASICs).

https://www.seeedstudio.com/Sipeed-MAIX-I-module-WiFi-versio...