Ok, haven't done this myself but here you can find the tools and How to.
SASPlanet: [Only registered and activated users can see links. Click Here To Register...]
How to: [Only registered and activated users can see links. Click Here To Register...]
For NNGraster there is a link that actually works under "Collecting the software" in the How to. The other link provided for SASPlanet doesn't work, so use the one I provided above and you get access to zipped files that work (no need to install).
As I said before, I haven't done this myself, but was wondering if you can use raster maps alone in a country where you cannot find the .fbl map. Will IGO work with rasters alone? I guess the fbl file contains other data that maybe important for routing, right?