3.5mm Headphone Adapter Cable for Nintendo Gameboy Advance SP – SupremeGameGear
Amazon.com: GBA SP Headphone Adapter, 3.5MM Headphone Jack Adapter for Nintendo Gameboy Advance SP(Allows You to use Your Standard Earphone on GBA SP) : Video Games
GBA SP Headphone Jack Adapter #shorts - YouTube
3.5mm Audio Jack Headphone Adapter Cable for Nintendo GameBoy GBA SP & NDS | eBay
Remember that time Nintendo got rid of the headphone jack? | Ars Technica