If you have an original DS or 3DS, you can use a flashcart (like an R4) or custom firmware (CFW) to run the ROM directly on the hardware.

For many Zelda enthusiasts, the Game Boy Advance era was a golden age of 2D top-down adventure. Among the titles released during this time was The Legend of Zelda: A Link to the Past & Four Swords (2002). While the "A Link to the Past" portion was a faithful port of the SNES classic, Four Swords was a revolutionary multiplayer experience.

Look for "DSiWare No-Intro" collections. This is where most "lost" digital media is preserved legally for archival purposes.

Searching for a "free ROM" of for the DS specifically refers to the Anniversary Edition