First of all you should use the 
Garmin WebUpdater (free download from garmin.com) to restore some functions, language files etc. - maybe the basemap also will be restored. If not, you can use every Garmin basemap you find (e.g. from nuvi etc.) - the basemap isn't so important for function of device, only for overview in big scales needed.
Unfortunately our links for 
Worldmap v5.01 don't work anymore, but you can ask bam-bam, if he can upload it again.
To the need you can download this 
- Code:
 http://www8.garmin.com/support/download_details.jsp?id=3645
Extract and copy 
gmapbmap.img from subfolder 
\GarminMobileXTFreeBasemap_4xxxx\GMobileCard\Garmin\ to 
Garmin folder on device. It's a very small and simple non routable basemap, but it does it's work.