I can't find any shop to buy a card.
Buy it online.
Unfortunately, Ray-Traced GPU acceleration is now obsolete. As are the GPUs that are on that list. The GeForce GTX 600- and 700-series GPUs have been superceded by the GTX 900 series, which lack the Optix library support that the Ray-Tracer requires. Adobe has discontinued the further development of the feature in AE in favor of the entirely software-only Cinema 4D engine.