I need a longer wire for my recently purchased Eris E3.5 speakers. What should I replace it with? Gauge? Specs?

Yes, I also need a longer speaker wire. Where can I get that? Amazon? I tried Best Buy and Guitar Center. The lattter didn't have it at all and all BB had was 30+ feet. I don't need quite that much. Just a foot or two longer will do...10' max maybe. What gauge should I be looking for? Any other specs I need to know besides just "black/red speaker wire"? Thanks!