Hope a few people find this to be useful.
This map is for the NV-U53/U73T/U82/U83/U92/U93T. At first I thought there are no maps for these devices in the wild, but after a long search I found this link:
All credits go to Cebu for posting it on that forum, I merely repost here for reference.

How to get the map on your Nav-U device:

The original post linked above does not give any info regarding this, so I'll try to give you a quick guide:

First, when you downloaded all the map pieces, unrar them and you'll get 2 files: EuropeB_Sony07B.map and maps10.bin.

You need to install ActiveSync on your PC from the installation CD that came with the device. If your device does not have 2GB internal memory, get a MemoryStick Pro Duo card and insert it into the expansion slot at the bottom of the device.

Connect the Nav-U to the PC with the USB cable, and turn it on. ActiveSync will recognize it and offer to pair with the device for synchronization, you can press Cancel as it won't work for the map transfer anyway.

Now, press Explore in the ActiveSync window, and a new window will open with the contents of your device's memory. If you have inserted the MemoryStick already, there will be a folder named MemoryStick, open it. Now drag&drop the 2 files you've unrar'ed before.

Do not worry: the copying took me almost 12 hours (!!), and the progress bar in the copying window does not update, at least on my computer. THIS IS NORMAL, just wait it out and eventually it'll finish.

Don't let your PC to go into hibernation or standby (check your Power Saving settings if necessary), or you'll have to restart the whole copying process again.

After the copying finished, you can select the Europe B map from the device's Settings menu.

Best of luck!