You're already likely familiar with using site:superuser.com to limit your query to a single website. For example, typing this into the Google search box limits your search to superuser.com:

reboot site:superuser.com

Now, you can use the OR operator to add another site to your query:

reboot site:superuser.com OR site:android.stackexchange.com

You can try the above searches with these links:

• https://www.google.com/search?q=reboot%20site:superuser.com
• https://www.google.com/search?q=reboot%20site:superuser.com%20OR%20site:android.stackexchange.com

Bookmark the resulting link after changing them to your websites of choice, so you can run other searches later without having to type everything again on your tablet.