I got you covered.
or
The bartender offers him a warm smile and says, "For you, no charge".
or
"A complex world demands complex hair."
or
Only one, but it may take upwards of five years for him to get it done.
or
None. There never was any light bulb.
Notes: Probably the only really good light bulb joke of 1984.
or
It went back four seconds!
or