They used to sell it in Morrisons but I can't seem to find it now. It used to be with the Jamaican foods so I thought maybe one of the little international stores on SGR would have it?
It's rare to see it anywhere in London. Try Rosslyn Deli in Hampstead, they stock lots of American foods or Selfridges food hall which is crammed full of treats from the US.
Comments
http://www.eggnogrecipe.net/