I'm also looking for a Symbian Ovi store mirror but I found no one.
Instead, you have some other symbian appstores :
- first the Opera Store, which is the official successor of Ovi store => not all apps were migrated
- the Symbian developpers appstore => make a backup asap, it will close soon !
- the currated appstore of stevelitchfield => most of the app are available for free, some links point to the ovi-store, and some apps are not free
- the Lucas Facana appstore => not updates since last year, but at least the soft is free, and it's easy to make a mirror of the server.
- the schumi1331 appstore
- and finally, there is this kind of website all around the web.