Kobo Books
Ingram Spark
$25 to list an ebook but those I have listed there have been happy with their sales so maybe.
Apple
Apple eBooks (iTunes Connect) – you have to have a Mac to upload it and it is a bit complicated and their payments aren’t great and if you decide to publish with them, let me know, the epub file will need a small adjustment just for them.
https://support.apple.com/kb/ph2808?locale=en_US
Barnes and Noble Nook Books
https://press.barnesandnoble.com/
Firebird Media Management 