Ah! That must be it.
7 seconds sound clip from the Dumbo (1941) movie soundboard.
You can hear this line at 00:07:11 in the Blu-ray version of the movie.
Quote context
[...]
- Now, let me see. Must be right around here somewhere. I hope.
(humming: Rock-a-bye on the treetop)
- Where are we? Oh, here. Highway 61, four miles to the gas station, turn left...
- Well, little fella, let's get going.
- Mrs Jumbo. Oh, Mrs Jumbo! Calling Mrs Jumbo. Mrs Jumbo? Oh, my.
- Mrs Jumbo! Oh, where's that Mrs Jumbo?
- At last.
[...]