for the hardware, maybe you can check this TaoBao site. 树莓派Raspberry Pi4B HIFIDiGi无损数字播支持DSD64 128 256 512-淘宝网 (taobao.com)
They provide suitable clock and parts, including chassis for your purpose.
I got one from them but with modified clock only. Because I’ll output thru USB to an OCXO DDC for i2s. A new and modified Pi 4 for endpoint of a new Roon user - Audio Gear Talk / Raspberry Pi - Roon Labs Community
