I ordered five of these little boards back in 8-17-2016 from a seller on Aliexpress. They took a month to arrive (not unusual when ordering direct from China). They cost me $2.01 each, with free shipping. Amazingly they even threw it the strip of 40 header pins to allow you to solder it up and put it on a breadboard. If you are in a hurry, you may be able to get them from domestic sellers on Ebay for a few dollars more. But, what's the rush?
Looking back at the site, these are now selling for $1.76 each, free shipping. I could have waited 30 days and saved 25 cents, who would have known?
Tom's Computer Info / firstname.lastname@example.org