Sign in Front Page with password lock

TINY JOB Simply, the site [login to view URL] is being created for use by a barter exchange group of specific people so the site isn't going to be open to the general public. There's no point in allowing the general public see contact information and products but more importantly, I want to prevent people that aren't affiliated with the group known as ITEX members to post listings here. What I need is something simple such as a pop-up screen which requires a password before entering any area of the site (see attachment of sample). I was going to just use my Cpanel lock but I want something that allows a bit more cleaner look specific to the site and would explain why a password is required. If the visitor doesn't know the password, the link that when clicked, it will send the single password used for everyone to the email address provided. This way we atleast know if the site is abused, we will have an email address we can black list in our admin. If you have any additional ideas about this that might be an improvement, please let me know. I need to keep my budget low on this one though please. Feel free to ask questions or PM me if you would like to chat about this. I'm sure a free java or php script can be found for this. I really don't want to pay more than about $30 for this if I can avoid it. Thank you, Michael Baker Project Management USA