where to get the official invitation letter and how much it takes

Dear Sir/Madam,
We are Easy Yemen loop International exhibitions company from the Republic of Yemen in Sanaa.
As the current situation in Yemen is known internationally and because of the tragedy situation in Yemen, the Yemeni Business Men are having troubles and difficulties of getting the Chinese Visas for coming to continue their commercial activities. and as before the Yemeni Business Men used to get the Chinese visa on embassies in Yemen, but now they need official invitation letter so we would like to cooperate with you, would like to know how long it takes to get official invitation letter, we are interesting to deal with you on issues official invitation letter visa business Visa, all about business people in Yemen husband travels a lot to China, how much is the invitation?
the Chinese products in the Arabian Peninsular
Waiting for your kind response
Best wishes & Sincere regards
Yours
Abdulhameed Ghanima
G-Manager
Mobile: 00967-711444192
Tel: 00967-1-486536
Mobile: 00967-770350377
Sanaa - Rep. Of Yemen