Invitation Visa

Ahmad, an invitation letter from the manufacturer may not be enough. You also need an an invitation letter from a duly authorized unit and your business part can get it for you.
In order to apply for a business M type, you should first prepare passport and copy of its data page, the application from, a passport-style photo, an invitation letter of a duly authorized unit and an invitation from business partner, a guarantee letter from your company and copy of its business registration certificate, recent 6-month bank statement, round trip air tickets and hotel reservation.
Next, submit the application to the embassy of China.

Dear Sir,

Kindly advise, is there any difference between business M and visit L for China?

Please inform the requirement of visit L

Kindly also provide the details of some travel agent who deals the tourist visa of China in Lahore, Pakistan

If you go to China for sightseeing purpose, you need a tourist L type. If you go there for business purpose, you need a business M type. To get the L type in Pakistan, you need to book a tour from a travel agency, and then apply for a group tourist L type for China. The required documents include an introduction letter from the travel agency, the application form, a notification letter from an authorized Chinese travel agency, as well as your passport and copy of its data page.