You can record the sound and vision separately using modest equipment, dump them into your computer with appropriate software and then mix sound and vision together. I use a cheapish DVD camcorder for video, which I import into my Mac with iMovie HD (free with the OS). I use an external recorder for the sound, which I import into the Mac using Audacity (free software), tweak the sound file to create an mp3, and then synchronise sound and vision with iMovie. Sounds complicated but, after a bit, it's not. There are all sorts of varaiations possible, from cheap to expensive. There's some info about what I do myself on my
website - not for everybody, perhaps, but you might get some ideas.