The victim was attacked at about 3am on Tuesday last week in the Tibetan Peace Garden, which is next to the museum off Lambeth Road in Southwark.
Officers today said they want to speak to Eleas Alfa Patience Godwin, 43, and urged the public to get in contact if they spot him.
The force said in a statement: "He is of no fixed address and his whereabouts are unknown.
"He has been known to frequent homeless hostels in the central London area.
"Anyone who sees Godwin is asked not to approach him but to call 999 immediately."
Anyone with information is asked to call 101, quoting reference CAD 2926 of October 15.