NEW YORK/FRANKFURT (Reuters) – Warren Buffett’s Berkshire Hathaway Inc (BRKa.N) said on Friday it had agreed to buy German motorcycle apparel and accessories retailer Detlev Louis Motorrad-Vertriebs GmbH for a little more than 400 million euros (297 million pounds). The purchase enables Buffett, known for his optimism about the United States and the investment opportunities it offers, to expand in Europe despite its economic problems.