Hi,
There is an application known as 'Mobile Atlas Creator' for the PC. Using this you can download maps on your PC and convert them for your mobile application. There are 2 j2me apps that work with this.
Mobile Trail Explorer
mobile-trail-explorer - Project Hosting on Google Code
TrekBuddy
TrekBuddy - J2ME application for offline GPS tracking
Try both of them and find out which works best for you.
Mobile Atlas Creator can be found here.
Mobile Atlas Creator