Stick to well-known community sites like Vimm’s Lair or the r/roms Megathread . Avoid any site that asks you to download an .exe or "Download Manager" to get the file.
Here’s the deal: because it was never a physical cartridge, you won’t find a standard .nds file that works on every old emulator. Instead, you'll likely come across it as a file (for 3DS homebrew) or a .dsi dump. Quick Tips for Your Search: zelda four swords anniversary edition rom