Sometimes it just has to be small. For this use case HiFiBerry has build the DAC+ Zero, that fits perfectly onto a Raspberry Pi Zero. It does not have the advanced features as volume control, EEPROM, ultra-low-noise regulators, but still offers a very good sound quality and 192kHz/24bit playback.
This is their smallest board in the Raspberry Pi Zero form factor. It can be used with the Raspberry Pi Zero and Zero W, as well as all Raspberry Pi models with 40-pin GPIO header (Only original A and B models have 26-pin headers).
but also with the bigger Raspberry Pi B+/2 and 3.