You can buy rubles at ICBC. You can choose foreign exchange trading, then choose the ruble you want to buy and enter the amount you want to buy.

Foreign exchange, named Foreign-currency in English, is a creditor's right held by monetary authorities (central bank, monetary management institution, foreign exchange stabilization fund and Ministry of Finance) in the form of bank deposits, treasury bonds and long-term and short-term government securities. Can be used when the balance of payments is in deficit.