Old panda photos

Does anyone have any photographs of Richard Nixon’s pandas Hsing-Hsing and Ling-Ling, residents at the National Zoo (Washington D.C.) from 1972 to the 1990s?

I have a chapter on them in my book (which I have now finished bar finalising the illustrations, sorting out references and putting together an index) and I would really like a photograph of these very famous pandas, especially one taken by a member of the public.

Whilst I am asking, I would also be interested to hear from anyone with photographs of Chi-Chi, London Zoo inmate from 1958 to 1972.