Update on my research. I sent a Jaguar dealer an email on a Sunday asking how much for a new DVD. Instead of a reply, I got a phone call from a salesman (he left a voice mail) telling me "you can call the parts department, but that's really not want you want to do. What you need to do is come in and see me, trade in your 2003 model and buy a new one. That way you get the latest navigation DVD". Jeez!
I found the company that makes the software and you can order updates on their website. http://www.navteq.com/index.html
Well, unless you own a Jaguar. Once you fill out the information on the make of your car a message tells you "contact your local Jaguar dealer".
I found a couple of the DVD's on Ebay but they were all the same year or one year apart from mine. One of these days I'll check with the Parts Dept. at the jaguar dealer, but I suspect it is going to be 300 bucks or more and frankly, it's not worth that much to me right now!