The souvenir book to Nicholas and Alexandra is readily found on eBay, but I haven't seen it in any version aside from English. You can take a peek at it on my website, if you haven't seen the English version before.
As for Assassin of the Tsar, the only new thing you can get for that is the new director's cut. Finding memorabilia for Romanovs: An Imperial Family is harder then finding the film itself. I don't think there was any memorabilia issued for this movie, but I could be entirely wrong.
If you happen to find anything, let us know!
