Wikimatrix.org provides a comparison of solutions. Here are hosted solutions that support wysiwyg, your own domain and custom branding (minus Wikia):

https://www.wikimatrix.org/compare/BrainKeeper%2BCentralDesk...

Use the wizard to narrow down choices.

These options look like the highlights to me:

Zoho Wiki: https://www.zoho.eu/wiki/pricing.html

PBwiki: https://www.pbworks.com/wikis.html