Hi,
Another option is to create one menu item of the type "hikashop product page" for each product. Then, you can use the URL of the menu item as canonical URL of the corresponding product. And thus, you can use the "menu assignment" system of the Joomla modules manager to restrict the modules on a more fine grained approach. But that requires a lot of overhead.
Another option is to use Modules anywhere:
regularlabs.com/modulesanywhere
With it, you could add the module in the description of the category, and activate the menu item's "show description" setting to display the description of the category at the top of the products listing, which would then include your module.
This is free, but you're limited in where you can place the module on the page.
Another option is to modify the template you're using to display the module position on the page only when the page is not a product page. You can do that with a bit of PHP in the index.php file of most Joomla templates. But if you use a template with a page builder, or some kind of heavy framework, you won't be able to do that easily. And when I say easily, it still requires a bit of PHP skills.
That's all the solutions I can think of. As you can see, there are free solutions, but they all have one downside or another. Using Advanced Modules Manager is the easiest, but yes, it costs a bit of money.