As oerkelens tells you, with your help is the ordinary idiom here.

I advise you not to use the term monopolistically you ask about in your Comment. This is a strongly negative term in most contexts; it signifies domination of an entire market, not a single customer.

What you probably mean is

We negotiating with the Ministry to make your firm the exclusive provider of the raw materials ...

As oerkelens tells you, with your help is the ordinary idiom here.

I advise you not to use the term monopolistically you ask about in your Comment. This is a strongly negative term in most contexts; it signifies domination of an entire market, not a single customer.

What you probably mean is

We are negotiating with the Ministry to make your firm the exclusive provider of the raw materials ...