The legal and recommended way to obtain these files is to "dump" them directly from your own physical Nintendo DSi console.
Some community archives, like those associated with BizHawk, provide documentation on the required hashes for "clean" dumps, though you must still own the console to obtain them legally. Setting Up DSi BIOS in Emulators
Disclaimer: This article is for informational purposes only. You should only use BIOS files dumped from your own console. dsi bios files download
your DSi while holding A + B to enter the Unlaunch menu. Run dsibiosdumper.nds from the application list.
Experience the original health and safety screens, followed by the classic interactive DSi main menu dashboard. The legal and recommended way to obtain these
This is the DSi NAND dump, which includes the full system menu, settings, and camera functionality.
What (Windows, macOS, Linux, Android) are you emulating on? You should only use BIOS files dumped from your own console
The firmware file for the ARM7 co-processor, which handles low-level tasks like audio, touch input, and Wi-Fi communication.