They are really very easy to make yourself. DC's bakeries have left me underwhelmed, so that's what I do! I use the Buttermilk Scone recipe by Delia Smith, who's an authority on British cooking.
http://www.deliaonline.com/recipes/type-of-dish/sweet/buttermilk-scones-with-west-country-clotted-cream-and-raspberry-butter.html
Clotted cream is easier to find, I've seen the Devon Company jars in Whole Foods/ Dean & Deluca - you can even order it on Amazon. Not the fresh stuff you can get in Cornwall, but tasty all the same. If you can't find it, whip some mascarpone and cream together for a decent substitute.