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The last map update released for the X3 series was in 2009-2010. The cards are hard to find, expensive.. And even if you can find them you are loading 6 year old maps which wont reflect any new road changes, intersections, etc.
Your best bet would be to consider purchasing a newer unit, that has lifetime map updates included so you never have to pay for maps. My vote is with Garmin. While some of their models do sometimes have issues. They actively support their products and release several updates to their maps each year. A new, entry model device with lifetime updates costs 100$ new. http://amzn.to/1L1qLhJ
With that being said, you can get a simple and older used model of garmin for 25$. http://www.ebay.com/itm/Used-Garmin-GPS-Satellite-Maps-Nuvi-260W-/400998053684?hash=item5d5d58b734
The 260 was an excellent model of Garmin. The only problem with going with an older unit like that is the map updates are expensive. For instance, a one time update from garmin costs 60$. https://buy.garmin.com/en-US/US/maps/on-the-road-maps/city-navigator-nt/city-navigator-north-america-nt-lower-49-states/prod28765.html
So even buying an old used unit, you still come out to about the same cost as the new unit I recommended. Except the new unit has lifetime free maps, and a 1 year warranty.
If you have further questions or concerns, let me know.
Dustin S.Senior Technician and Network Switching Systems Operator / Maintainer.