It use to be viewed and bought through the All Products page, which wasn't easy to find to begin with (small link at the bottom of the main Adobe website page) and then on the second page of that section. But it seems Adobe has removed that.
So it seems to me that Adobe has finally stopped selling any stand alone version of LR.
You can continue to use LR 5 as long as it works with the operating system you use on your computers. If you need newer camera support you can use the Free Adobe DNG converter program to convert the native RAW image files from your new camera to DNG files which will import into LR 5. Or you could switch to shooting JPG's.
Or you could sign up for the subscription based LR + PS plan.
Or you can move to some other image editing system.