I would say that your only other tang options are going to come from the zebrasoma family with that size tank. I would not put two Ctenochaetus tangs in together. You will get others to say that you shouldn't add any other tangs to a 4' tank, but if you are going to do it, I would stay with one of the smaller zebrasomas (yellow, purple, etc)
On another note, I have personally found tomini to be aggressive, so a new tang may not do well if added after it. I had a tomini kill a goldflake angel once.