I'd look into your family tree more carefully, as there may be a tartan to which you have a claim to wear. Also, I wouldn't limit myself to Scottish ancestory: you may have Irish or Welsh Ancestry as well.

If that fails, then I would go for a Universal Tartans that you find makes the most sense. Remember, there are also no tartan police to worry about.....but you wouldn't want to offend your forefathers if you descend from a kilted family line.