Thanks to the help of Brian Boyd and SES, I was guided to the photographer’s picture of VN by “Lord Snowdon, … taken in December 1972, appeared in Saturday Review of the Arts, January 6, 1973, and is mentioned in VNAY 609.” This indication was sufficient to orient my search and, to my surprise, I found the data I’d been looking for in the VN-L archives, including VN’s words related to the soulful image wrapped in a poncho.
Cf. https://listserv.ucsb.edu/lsv-cgi-bin/wa?A2=nabokv-l;cc97819c.1003
Brian Boyd "Vladimir Nabokov, The American Years" (Princeton University, 1991) p.609, VN aged 73: "Early in a foggy December, Lord Snowdon arrived to photograph Nabokov - a month after Youssuf Karsh had been on a similar mission - for the special issue of Saturday Review of the Arts. Nabokov enjoyed Snowdon's company as he clambered up to the hotel roof or stopped on a mistily soulful hillside, in shops, cafés, and restaurants, and back in his office, to pose for one of the most diverse porfolios of portraits any photographer had assembled of him." [ ] "Vladimir Nabokov, Selected Letters 1940-1977," Ed. D.N and M.Bruccoli (A Harvest/HBJ Book) p504 to Edmund White (1973): "Many thanks for this beautiful New Year gift (note: The January 1973 issue, which included VN's essay "Inspiration," Lord Snowdon's photos of VN, and critical assesments.) You have never set eyes upon me, and yet, by a flash of inspiration, you chose from the porfolio my best likeness for the cover...and that the picture on p.43 (poncho plus a dream of infinity) is a no less amusing parody of the Argentine dreamer...
Now I could also reach a link to the Saturday Review of the Arts is http://www.unz.org/Pub/SaturdayRev-1973jan06-00038
Other texts are accessible below:
Nabokov
by Edmund White
, p. 33 - PDF
by Joseph McElroy
, p. 34 - PDF
by William H. Gass
, p. 35 - PDF
by Joyce Carol Oates
, pp. 36-37 - PDF
ˇ Nabokov
by Lord Snowden
, pp. 38-43 - PDF
by Simon Karlinsky
, pp. 44-45 - PDF