Sure, they exist. They are regulated and not for reproduction/sale. The last on I saw "become available" was in 2011 and it went for some in the neighborhood of $1000, if I remember correctly. I expect if one "popped up" today, it would likely sell for something >$1k.
Over a decade ago, I contacted both FN US and Belgium headquarters looking for one, providing my Type 7 FFL and Class II SOT. I even provided the NSN for the manual I was looking for. US office told me they don't have any and didn't have access to get one (same with FNC armorer's tools) because they were never produced in the US and to try Belgium. Belgium told me they were only available to militaries, not manufacturers or gunsmiths, and I could not have one imported. When I told them I was doing work on FNCs that we legally imported in the 1980s they essentially said "sorry, can't help you, try the US office"...
Basically, if you do find one, it likely came from an unofficial source that somehow made it into private hands. Also, they were produced in Dutch, French, and English, from what I remember, and I think English was only done due to Belgium being part of NATO. So if you do find one, there is also a decent chance it wouldn't be in English.