New VISA to China

Hello,
We are two dutch travellers staying in China right now and we have got a Chinese L type only for 15 days (Vietnamese policy they told us..) Now we are going to Japan for two weeks, before returning to Beijng where we will take the transsiberian express within a week. So we would like to apply for a new L type in Tokyo. Would this be possible and do you maybe have a list of travel agencies working with you?