Check out Influads.com - very targeted display advertising for your target audience. CPM's are slightly high though. If you can pull a .5% ctr you would probably end up paying ~$1 click (note: I WOULD not try CPM media buys BEFORE making sure it converts with CPC first).
Shoot for an optin rate ~45.1% at least (if this is hard straight out the box, just have 1 data field, i.e. email address not name+email address)
Profit hack: consider a funnel like this:
squeeze page-->immediate redirect = sales page-->sales page thank you has something like PayWithATweet.com on it...offer a bonus for a social share.
Right now it is just a matter of figuring out where to spend my time.