Where is the fuse relay for a cigarette lighter in 1991 Honda accord not under hood and not underdash and radio works not on any diagrams either?
The cigarette lighter does not have a relay. It does however have a fuse. It may use the same fuse as the radio. If all fuses are good, suspect the lighter itself is bad. Try your lighter in a know good lighter receptacle. If it works there, then suspect the lighter receptacle in your car is bad.
My Haynes repair manual for model years 1990 through 1993 states that the cigarette lighter relay is found in the left end of the dashboard below the PGM-FI relay.