Geo IP Blocking Script

I am a small business owner, just me and my wife and I need to install a Geo IP block on my website. Due to copycat competitors I want to limit access to my site when a visitor is coming from a particular country. I will also need a control/login page that will allow me to easily turn this block on and off when needed. I see online that there are some OpenSource programs and there is a paid database update program provided by a software company. I am not sure which is best, but If I can block 99.5% of most common computer users in country who do not know how to use proxy servers, I would be very happy. The page the visitor receive from a blocked country should be simple 404 error page. Please note that I built my website in iWeb and I want to avoid adding IP blocking code to my individual iWeb files, as this would not allow me to make updates. I am hoping that I can upload the Geo blocking files to my server independently. Thank you