I've Got It !
There was/is a Betty Boop character that would say this, but with much forethought type fanfare.
..."Oooo...let me think....hmmm...ah ha.....oh ha ha I've got it!".....
And a big lightbulb would go on over his head!
After a search, because I forgot all the details, except the quote, his name was Grampy. I have gone back to that lightbulb moment, inside my own head, over the decades. And today when I was thinking about something around the house to blip. Then "Oooo...let me think....hmmm...ah ha.....oh ha ha I've got it!"..... A double lightbulb moment!!
I was not fortunate enough to have the 'thinking cap' with 'lightbulb' attached but I made do with the light from my iPhone.
Album: Chants Of India, Ravi Shankar, Excerpt-Veena-Murali
YouTube Video: 3Hours of Amazing Nature Scenery On Planet Earth.