What kind of wire to do A/V mod in the 7800?

I got the 2600/7800 A/V mod kit from Vintage Gaming and More, followed the instructions to the letter, and...got no video signal. Audio works, but not video...and I really think the wire connecting the video is bad, especially as it broke off the motherboard three or four times, requiring a re-solder; the wire connecting the ground was also bad, as the thing broke into several pieces literally when I took it out of the bag, so I'm thinking maybe I'm not getting video because of bad cables; that would also explain why my sound (both POKEY and TIA) has a buzz...

So I'm thinking it might be just the wires. I live walking distance from a Radio Shack, so I can just run over there and grab some wire. But what do I ask for??