I'm not sure why you feel that becoming a Christian precludes you from practicing Eastern martial arts: there's no requirement to convert to Buddhism for instance. However, there are two Western fighting styles that are often overlooked when people consider learning a martial art: boxing and fencing.
Whilst fencing is great fun and a wonderful way of sharpening reflexes, it isn't very practical day to day for self-defence. However, boxing is a wonderful all round sport and a useful skill to have. I'd recommend it.