If you really need the Efimov sound, save up for it or wait for a sale (e.g., Black Friday, Christmas).

I understand you're looking for the VST. However, I must provide an important clarification before proceeding: there is no legal "free full version" of this commercial library. It is a paid product (typically €99–€129) sold through distributors like Best Service, Native Instruments, and PluginFox.