The book- The Cathedral of St. Peter and St. Paul, The Burial Place of the Russian Imperial Family [Gendrikov & Sen'ko, Liki Rossii, St. Petersburg 1998] has pictures of these memorial wreaths. I have never seen such pieces catalogued in any Faberge book, but I am also no expert.
The book states that the memorial of Alex. III had 674 of these, and that over 30 boxes were crated and sent to Moscow after the revolution [1919]. Apparently, they have been lost. Guess is that they were melted down.