I lost a Clown today

[gregzz4]

Because your current clown is the Boss, I'd recommend adding a smaller one.
This will minimize fighting. Even though the current one may not have been in charge, it's still the boss of the tank now.

As far as waiting I can't say. I'm sure there's a grieving period but there's also a period where the current fish will stake too much territory and not allow other fish.

Personally I'd just add one right away, barring a QT cycle.

I know, not much help but rather you had some info vs none.