Livre d'Or

If you don't mind getting fancy, the afternoon tea at the Georgian Room in the Fairmont Olympic serves proper Devonshire cream with their scones: http://www.fairmont.com/seattle/dining/thegeorgiantea/

The other Seattle tea locations I've been to that have scones, but not clotted cream are the Queen Mary (whipped cream), the Sorrento (mascarpone) and Remedy (butter).

I haven't been, but I think you can get scones and real cream at the British Pantry, which is in Redmond:
thebritishpantryltd.com