Codeko

With this plugin you can set any post type (or posts types) as parent of any post type.
Urls will be wellformed, redirects will work, breadcrumbs will work fine.
This plugin is recomended when you need a url structure with a mix of post types. Any url structure you can imagine could be done.
Post types rewrite slugs will be ignored

Custom Posts Parents

Set any post type (or types) as parent of any post type. Any post structure can be created with this plugin.

pantsonhead

Currently WordPress does not provide the ability to change the post that an item in the Media Library is attached to after it has been set. This plugin allows editors to change the parent post to another post.

Change Media Parent

Allows editors to change the parent post of an attachment after it has been set.

Custom Posts Parents vs Change Media Parent