There is exactly one. You can ZFS send/recv to and from an rsync.net account that is enabled to do that:
https://arstechnica.com/information-technology/2015/12/rsync...
https://www.rsync.net/products/zfsintro.html
OR you can get a plain old rsync.net account and do a "dumb" sync to it and just configure ZFS snapshots on any schedule you like.
Ask about the "HN Discount".