There is "Google Contributor" [1]. The idea is basically that you pay the publisher out of your own pocket for their ad space, to buy your own impression. This

There is "Google Contributor" [1]. The idea is basically that you pay the publisher out of your own pocket for their ad space, to buy your own impression. This might be a great product if it covers the majority of ad inventories... [1] https://en.wikipedia.org/wiki/Google_Contributor https://en.wikipedia.org/wiki/Google_Contributor