Write a Software Requirement Specification (SRS)

I want someone to write a SRS for my project. We have an idea and goal but hard for us to write a detailed SRS to provide to the developers. I want someone who understands the idea, looks at all the examples of other websites that we provide and make a SRS based on that. Here is what we want:

1.Functional & Non Functional Requirement analysis

2.Use case documents

3.Project proposals for client projects

4.Software Requirement Specification including;
- Use cases diagrams
- Class diagrams
- ERP diagram
- Sequence diagram
- Activity diagram
- Flow Diagrams