Get a juvenile clown - one that is smaller than Sharkbait. I believe juvenile clowns are not of either sex yet, so by picking out one smaller than Sharkbait, you'll be getting one that doesn't "challenge" Sharkbait and they should live harmoniously. (clever name, lol!)
I've looked at your tank info - is this a 10 gallon tank? I think that with the three fish you have now, the tank is at its stocking limit. If everything is going well with this tank, I would not upset the balance. I would wait to upgrade to a bigger tank before getting another clown.