RealPlayer Beta for Android works great on my Kyros 7022. I don't have access to the Android market, but it is a direct free download from AppsLib. It does more than play just .avi it plays other video and audio formats as well.
you may try mobo player, it's one of the best android players, but i can't make sure it can play all the avi files. as far as i konw, avi is a container format, it can contain different video and audio codec. Not all the codec supported by mobo player. so the playback with some issues. However, you can convert avi to h.264 mp4, which is friendly with most tablets