How can a SharePoint Online wiki page library be migrated to another SharePoint Online tenant?

We are trying to move a SharePoint Online wiki page library from one SharePoint Online tenant to another (Office 365). There is no functionality within Sharepoint to do this, and it is too expensive to use a third-party app.

We have tried the following:

• Microsoft’s SharePoint Migration Tool does not support SharePoint Online to SharePoint Online migration.
• We have looked into Mover (https://mover.io/ – acquired by Microsoft) and are currently resolving some global administrator access issues for it. (Results pending)
• We have seen many suggestions to create a template of the site, but wiki sites are publishing-based and cannot be created into a template.
• We have accessed the site files in Windows Explorer through the Sharepoint Classic interface (in Win7 Internet Explorer x32), but it does not copy site contents, only site layouts. Also, the destination site breaks / disappears when source files are removed or replaced with files from another site.
• We have used Powershell PnP to download and copy site files to another site, but it does not copy wiki pages, only site pages.

Has anyone had any success with this? Any advice/ideas would be appreciated.