Amazon.com: Mcbazel AV Cable for Wii Wii U, Audio Wii av Cable Compatible with Wii, Wii U and TV System,3 RCA Gold-Plated Interface,1.8M/6FT : Video Games
So, I got a Wii Component cable.. and I'm really impressed. See rather basic comparison photos against regular old Composite playing a GameCube game. I'd recommend a cheap Wii+Component (£20+£7) over GameCube+Expensive
Nintendo Wii / Wii U Composite Audio Video Cable - Walmart.com
AV Cable for Wii Wii U, Composite Audio Video TV connector Cable Cord for Nintendo Wii U/Wii - AliExpress
Nintendo Wii A/V AV RCA Audio Video Composite Cable Cord - Etsy
Only getting composite through Wii RGB scart cable : r/crtgaming
Nintendo Wii OEM RVL-009 AV TV Composite Cable (Red / Yellow / White) | eBay
AV Composite Cable for Nintendo Wii / Wii U® - XYAB