The Absolutely Worst Raspberry Pi Case : 8 Steps (with Pictures) - Instructables
hardware - What size screws does the Raspberry Pi board use? - Raspberry Pi Stack Exchange
Universal Raspberry Pi Hat Case+ Standoffs + Screws+ Nuts Diy Kit, Generic Case Kit For Raspberry Pi 4 Model B/ Pi 3b+ Plus/3b - Demo Board Accessories - AliExpress
Brass M2.5 Standoffs 16mm tall - Black Plated - Pack of 2 : ID 2337 : $1.25 : Adafruit Industries, Unique & fun DIY electronics and kits