Eliot's song of the Thames daughters appears in these places:
Note that the song first appears in The Waste Land on line 277 after a description of the Thames River (starting on line 266) and before another description of the river that starts with an invocation of Queen Elizabeth and the earl of Leicester (line 279.) Then another invocation of the song ends the description (at line 290.) This then is also at the start of the stories of the Thames daughters, Highbury, Moorgate and Margate Sands. Their stories end with the Thames daughters singing "la la" on line 306.
The "la la" is sung by the Rhine-daughters to Siegfried in Götterdämmerung but perhaps instead this was inspired by Das Rheingold where Wagner has the Rhine-daughters cry a lament of "Weh! Weh! as Alberich runs off with their stolen Rhinegold.
A part of Wagner's libretto to Das Rheingold is kept on the Exploring The Waste Land web site.