Bewinner I2S Interface HiFi DIGI DAC + HIFI DIGI Digital Audio Card for Raspberry PI B+ Model B 2B 3B PCM5122 DAC Output with Gold-plated 3.5mm Jack Socket RCV Double Clamp: Amazon.co.uk:
Adafruit I2S 3W Stereo Speaker cap for Raspberry Pi - Mini Kit - Boutique Semageek
DAOKI PCM5102 DAC Decoder Module I2S Interface GY-PCM5102 PHAT Format Player Board Digital-to-Analog Converter Voice Module for Arduino, Raspberry Pi with 3.5mm Jack Audio Cable, Dupont Cable: Amazon.com: Industrial & Scientific
The Raspberry Pi: Audio out through I2S | Dimdim's Blog