The ones from A&A (whether you get it from them or through KoA) should all be good. I'd particularly look for the "lugged" spears (like mine), since they were common throughout the period if I'm not mistaken.
Mine is over 8 feet long. It looks like the A&A spears tend to be a little shorter. But you could probably order one and request a longer pole, since A&A is pretty good about customization.