You could always make your own handler on your site, with a banner id and site id included in the url, and increment the click counter or add an entry into a database every time you get a click. You could then take it a step further and track whether or not the person clicks the "buy" button on your page after coming from an ad.
Of course, all of that requires that you set the ad link to go to your product page on your site. It wouldn't be terribly hard to keep up with that way, and you could see if you were getting false numbers from the ad host.
