This is a case for the ESP8266 ESP-01-based DHT11 module available via various sellers. For example, here is one that has the module and the ESP-01 as a combo.

I have noticed that the temperature readings of these devices tend skew high due to the heat from the ESP8266. To counteract, I recommend bending the sensor out so that it's no longer affected.

Power is provided by a micro-USB breakout found in the same places as the module. Here is a link to one from the same seller as above.

For software, I am using esphomeyaml on the device to log values to Home Assistant.

Update 2019-03-23: Adjusted the design to be a little larger to allow bending the sensor out to avoid skewed readings from the heat of the ESP8266.