I always try to buy 1st party accessories but I don't think I want to spend $50+ for an official one on ebay, so what's the next best thing and what should I avoid? Much thanks!
Play-Asia has the jp cables for $40. Your other option would be to call Nintendo's 800 number and ask if they have any. Sometimes, like with the Mario DDR restock, they'll get something in and it won't appear on the site.
It's a shot in the dark, but you might also want to check the used sections of your game stores. I remember reading that a couple people lucked out and found the cable for $10-$20 at Gamestop about a year ago.
You should probably go with ordering it from play-asia, though. It usually sells for $60+ after shipping on eBay.