I think you are seriously underestimating the demand for Sir David Attenborough plushies. The dude is up there with Neil Degrasse Tyson and Carl Sagan with the I Fucking Love Science crowd pantheon of science fandom.
Most British people have never heard of those two but Attenborough is about as recognisable as the Queen and with far more positive associations. He has been on the telly since the 1950s and his broadcasting is part of the shared culture, like the footage of him hanging out with gorillas...Less of a thing nowadays of course, but if you are British and old enough to remember when there were only a couple of TV channels, Attenborough is the Don.
Sir Attenborough is a wonderful choice, and I'm quite happy they named a research vessel after him. But Boaty McBoatface was a wonderful choice, too, and I'm very disappointed it was overruled by the fuddy-duddy bureaucrats.
Although I wouldn't want to encourage anyone to take the conventions surrounding the last vestiges of the feudal system too seriously, it's either "Sir David" or "Sir David Attenborough".