Futureebook has:
Here is today’s e-bestseller list with prices from major e-tailers. Prices supplied by Luzme.com (formerly ebookprice.info).
The FutureBook e-bestseller list is compiled by The Bookseller’s chart expert Philip Stone. He uses a points-based system based on e-tailer chart positions and estimated e-tailer market shares. It is compiled at the same time each week. This will be replace[d] by a more robust e-chart when it is available.
Thanks to reader Howard for the link.