Find a ds cartridge to play downloaded ds roms on your Nintendo DS (Lite) ? R4 cards, including R4 DS and R4 SDHC, will both meet your needs. Unfortunately, R4 DS card has been out of production since the late 2017, not available now.
R4 DS card with wood r4 or YSMenu kernel can run all ds games on DS Lite or DS Original, but compatible only up to 2GB memory capacity
R4 DS card with Kingston 2GB memory card combo, also provide software install service
R4 SDHC card is a DS card, designed for DS Lite & DS Original/Phat, compatible with YSMenu kernel and SDHC memory cards
R4 sdhc card pre-loaded with YSMenu kernel added into memory card, only need paste ds games to play