How to set a Custom Sidebar for custom post/page
You can create unlimited sidebars and set each of them for custom post/page. To do this you need to follow this steps:
1. Open Admin > Appearance > Sidebars.
2. Click the button "Add New Sidebar".
Enter the name of sidebar and click "Save Changes".
3. Go to Posts/Pages > Add New.
Input the Title, Content and in right section you will see "Page Customizer" and select the sidebar.
If there isn't available "Page Customizer" metabox, open "Screen Options" at top and check it.