no, it's not being sold anywhere. but if you can find the full canvas jacket control panel it will give you access to all of the best features.
really, by this time, you should be able to get a FREE copy.
I've never used it, never got it. not willing to spend more money on a video game that's this old with no tech-support or instruction manual to go with it.
just go visit
Society of WWI Sim Artisans and you'll get all of the hard work that other people did which helped make the FCJ possible.
this is not to belittle the accomplishment of what Kessler did with FCJ. I'm sure it was quite awesome. and he did all of the skins himself. but many of the models upon which he placed those most excellent skins, were made by other people--who offered up their hard work free of charge.
so... yeah, see if you can get a freebie from somebody who's already got it.