LONDON (AP) — Queen Elizabeth II lives on at the Cool Britannia gift shop across the road from Buckingham Palace. Four years after the queen’s death, the shop is doing a brisk business in mugs, tea towels and key rings bearing the likeness of Britain’s longest-reigning monarch as the nation marks the centenary of her birth on Tuesday. Items featuring her son King Charles III? Well, not so much. “We still sell more than the king any day,’’ said Ismail Ibrahim, the store’s manager. The late queen’