How can I source a technical co-founder?

As a developer and technical co-founder myself, if you've been through 8 developers then there is definitely something you are doing wrong, either content wise or communication wise.

Here are things that make me take pause:

A) unspecified, or shifting, idea of how the app/website will actually work

B) bait-and-switching (it "sounds" like a pretty cut-and-dried good opportunity, but once you drill down into the actual task lists of what *really* needs to be done, it is not crystal clear and they only find that out after they look at your functional requirements/specifications documents)

C) you yourself may not have a crystal clear idea of what it is you are creating and thus have difficulty communicating it to someone else

D) your "end target" is shifting too quickly for a developer to get a "fix" or a "handle" on

E) you are reaching out to developers who "code to spec" and instead who you need are developers to help you understand the technical details of the "big picture" and who have the understanding of your business process & can help you make decisions

F) you personally may have a communication block with coder/programmer types, especially those who tend to be very "nit-picky" and who need to understand on a very granular level what it is you are attempting to accomplish.*

G) Too little pay/equity in your offering? Good technical co-founders already have a boatload of potential opportunities, so what sets yours apart?

H) Are you looking at the right places? I like http://women2.com/ and http://angel.co

* For example, do you have a list of all the different types of data on the site and their relationships to each other? Do you have a sketched out list of all the reporting or display screens you need? Do you know what your metric of success on the app/website will be?

I think Monica's answer here is full of great insight.
It's highly likely that given that you've cycled through 8 developers with no product yet complete and marketable, that some of the responsibility lies with you in how you are communicating, setting work goals or otherwise interacting with technical talent.

Generally speaking, any kind of contract work is likely to produce less reliable work than from someone who is really bought-in to you and the product. That doesn't mean you can't get a good MVP out to market with contract labor. I've done it several times with good success.

In a quick call, I could help you understand what you might do to improve your ongoing relationships with a new developer, look at how to compensate and recruit talent in an MVP scenario, and also review the state of your MVP.

It sounds as though you might be close to getting to the next level, so I hope a call with me might help get you to that next level.