Johnson Davies designed and built this UPDI Programmer Stick based on an ATmega328P, that is available on GitHub:
This is a USB-stick sized UPDI programmer, for programming Microchip’s new 0-series and 1-series ATtiny chips from the Arduino IDE
It’s based on an ATmega328P, and is essentially an Arduino Uno on a USB stick, so you also could use it as a mini-sized Arduino Uno.
Project details at technoblogy.com.