If you're making a portable you probably need something to watch it on. (Unless you want to guess what's happening in the game, but I wouldn't advise that) Anyway, this forum is your "Hacking a pocket TV/screen" one-stop solution. Share your experiences and knowledge here.
Those should work, but thats from Hong Kong, so if you buy them expect to spend anywhere from $15-$30 for shipping. Your best idea is to just cheak around town, I know Radio Shack only sells 5mm so ask someone there if they know of another store around you.