I'm the one you are looking for is an original song created for Fallout 4 and performed by Lynda Carter, who voices the character Magnolia.  The song is played on Diamond City Radio and can be heard "Live" in The Third Rail bar in Goodneighbor.
I see you lookin' 'round the corner
Come on inside and pull up a chair
No need to feel like a stranger
Cause we're all a little strange in here.
Have you got a history that needs erasing?
Did you come in just for the beer and cigarettes?
A broken down dream you're chasing
Oh, I'm just the girl to make you forget.
So we're glad you dropped by
Come in and loosen up your tie
Have a drink or maybe just one more
But if you're searchin' for something to bring you comfort
Oh well, I'm the one you're lookin' for.
Now is your motor running close to empty?
Or are you runnin' from yourself?
Or are you thirsty for a brand new kind of pleasure?
Or are you hungry to be someone else?
So sit down your pretty face
You came to the right place
Oh, where every night it starts once more
I'm telling you friend, your search is at an end
Cause I'm the one you're lookin' for.