We don't have a password protected page feature, I am afraid, but for one-off pages the same kind of protection can be had using the existing native user accounts -
a. Temporarily create a user account placing it in the 'Authenticated User (special)' group
b. Set the access of the page to be protected to allow only 'Authenticated User (special)' (can be done from the Advanced settings dropdown in admin-panel).
Send the creds to the users who are allowed access. They'll need to input both the username & password to access the page, as opposed to only the password as in password-protected page, but I don't think that would be too much of a constraint.
Does this help?