Hi,
By default you can set a module under the product page, but this module will no be displayed in the sidebar.
You can maybe find a plugin which call a module in a certain position when you use a tag on the product page.
Or in the Joomla options of the module, add a suffix class, like:
Then in Configuration > Display > CSS, edit the frontend css file, and add the property: #onproduct{ display: none;}
And edit the view "product / show_default" (via Display > Views) at the end of the view add the code:
<script>
document.getElementById('onproduct').style.display = 'inherit';
</script>