"Let me look into that for you. Please hold and I'll be back in less than 3 minutes".
Did you like that? I heard it the other day when I called Delta Airlines, and I liked it.
It sure beats some of the alternatives: "hold on a sec" or "hold for a moment." And it solves the issue of having to come back to the call every 30 seconds to explain that you are still investigating.
Why not track your average 'on hold' times, set a standard you can beat, and give it a try.
Let me know how it works.