Au bout de moment signifie "after awhile "or "sometime later". Je dirais probablement "Je reviens tout de suite."

Je reviens tout de suite ! ;]

It could also be "de retour dans un moment" (back in moment). Beware but / bout (goal/end), not the same word!

Your translation is not commonly used. The issue of your sentence is too uncertain and the verb is not the right one. The proposition of Christian and Laura are just fine.