Where Can I find more clients for iOS Development Jobs?

Have you tried AdWords and a website/landing page for you or your business?

I know a company in Brazil that is doing exactly this:

* They have a website/landing page setup that explains how they charge for the application and has a call-to-action button to ask for an evaluation of the project the client have
* They have thought and described a way to evaluate projects roughly so that the client may have an idea of time / costs of the project
* Their website has images of applications they have developed before in a portfolio

They are doing great, actually they have more people asking them projects than they are able to develop and they started rejecting offers.

A friend runs a site called "Contract IQ" (www.contractiq.com). Suggest you list yourself there and find other such avenues to showcase your prior work so clients can find you!

Once you're good they usually come to you...
You might want to try reaching out to existing business in your area but it depends on what you have experience building.
If you have free-time, you might also want to consider creating a skinnable template to be sold to multiple businesses.