It sounds like you need an image management system like Portfolio. I use it to manage my images it stores a thumbnail and other information which is totally customizable using custom fields. That way you can carry all the info from your master database with you then you add the new info on location and it will tell you where your original file is locataed and pull it up for you. If the file tyhat you selecet is on a CD or DVD it will tell you which one to put in to the drive so that it can pull up the image. I have been using it for around a month and love it. It does so much more like slideshows , quicktime movies, web galleries, etc.
I use watch folders so that it automatically update the information from add stuff as you add it to your master directory. I make my backup on site on the CD/DVD if possible and use that for creating my working files that way I know my backup contains good information. Then I can add the files to my master library once I get home but currently I am using a WD Portfolio 120 GB drive that is USB powered and is about the size of cellhone ipen may a liitle wider and thinner and my cell phone is a Motorola Razor so it is fairly slim. No excuses for not taking the drive since it works of the laptop for power. It is totally portable and I create a backup of the library on another larger dive at home.
So if you use the Portfolio drive you can take it witho you I got mine real cheap on sale from Staples I thought it was $129 buck for the drive the sofwate from Extensis is around $200 and the conmbination is great for traking and storing your master library or a copy of it. Then sync when you get home.
I hope this helps.