Letter of invitation for Tourism

Greetings ladies and gentleman,

I am interested in a trip to Hangzhou, i have already purchased the plane ticket, and the hotel reservation for the 21st of January. Would it be possible to get a tourism invitation letter solely, what are my options to do so? Money won't be an issue for me. my nationality is originally Tunisian even though i live in Germany that is why i need the invitation to receive a visa. I await your reply, as i urgently need the invitation before the 7th of january.

Best regards,
Malek Khoudi