These ones are not from the Mexican State visit to the UK in 1973, but from the British State visit to Mexico two years later, in February 1975 - I hope you won't mind...
Queen Elizabeth II with Mexican President Luis Echeverria (right) during her visit to Mexico, 1975. (Photo by Serge Lemoine/Getty Images) (Source: http://www.gettyimages.fr/detail/photo-d'actualité/queen-elizabeth-ii-with-mexican-president-luis-photo-dactualité/139758690)
Queen Elizabeth II and Prince Philip with Mexican President Luis Echeverria during their state visit to Mexico, 1975. (Photo by Serge Lemoine/Getty Images) (Source: http://www.gettyimages.fr/detail/photo-d'actualité/queen-elizabeth-ii-and-prince-philip-with-mexican-photo-dactualité/138533710)
Queen Elizabeth II attends a banquet during her state visit to Mexico, 1975. (Photo by Serge Lemoine/Getty Images) (Source: http://www.gettyimages.fr/detail/photo-d'actualité/queen-elizabeth-ii-attends-a-banquet-during-her-photo-dactualité/138533709 and http://www.gettyimages.fr/detail/photo-d'actualité/queen-elizabeth-ii-during-her-state-visit-to-mexico-photo-dactualité/138533681)