usage - Difference between "search of" and "search for"

I was writing a classified for a company, but I got confused between two different usage of 'search'.

Read the following sentences:

If you're in search of a quality marketing company, then your search ends here!

If you're in search for a quality marketing company, then your search ends here!

Now, I want to know what native speakers say about the usage in above written sentences. Are they both okay? Why?

Thanks for your help.