I now remembered the provider of third PBS as a service, it's the German company Inett:
https://pbs.inett.de/
20 Euro für 1 TB backup space or 0,02 Euro per GB doesn't sound too bad imho. And although it's more expensive than the vserver route they will (like tuxis and cloud-pbs) maintain the PBS instance for you, saving you the hassle of administration. I might be tempted to switch to one of the three if my backups get to large for my netcup vserver
Like tuxis.nl and cloud-pbs.com they are based in the EU and I'm not sure whether they provide service to customers outside of it. As far I know tuxis only provides services to Companys outside of the Netherlands, but I remember (
@Jeeves_ @tuxis Can you clarify this? Thanks

) that they might know of a reseller in your country if you contact them. And asking never hurts in any case

You could also ask Proxmox Server Solutions GmbH via their office mail (
office@proxmox.com), whether they know of a PBS as a service provider in your country.