Englishman in japan

I am a uk passport holder and am in japan on a vistors visa, i have been invited to china by my family members working in china so i want to visit them at the end of my visit to japan. they have booked me tickets to china, but i am having a hard time finding a travel agent to help me apply for the tourist L without flights. can you suggest any companies? is it possible to apply to the embassy directly in this case?