Hello,
Regrettably, this can't be achieved with any small workaround in the current version. The products are considered as global objects and thus they are available within every site on the same Kentico instance. However we are currently implementing the differentiation of the
E-commerce module for every site, so every page will have it's own instance of the shop. That means also, that the products can be configured to show only for some sites or for all of them. This feature should be available in the next 6.0 version of Kentico if everything goes according to plan.
Best regards,
Boris Pocatko