One thing I've had good luck with is kindle unlimited since they have such great reach in the kindle market. (lincolncole.net)
The Amazon UK Kindle copy is on offer for a limited time and free on kindle unlimited. (mjmallon.com)
(If you compare the manx prize's book page to any of ours, you'll note they removed the «$ 0.00 with kindle unlimited» announcement from right by the ebook / paper price on every page. (madgeniusclub.com)