Hi,
The data used on the product page is loaded by the function "show" in the file components/com_hikashop/views/product/view.html.php
So if you look there, you'll see that the code loading the images and files data of the product is:
$query = 'SELECT * FROM '.hikashop_table('file').' WHERE file_ref_id IN ('.implode(',',$ids).') AND file_type IN (\'product\',\'file\') ORDER BY file_ordering ASC, file_id ASC';
$database->setQuery($query);
$product_files = $database->loadObjectList();
if(!empty($product_files)) {
$productClass->addFiles($element,$product_files);
}
Then, you can look at the file components/com_hikashop/views/product/tmpl/show_block_product_files.php which is where the download links are created based on the loaded data.
Finally, you can just edit the view file used on the listing (by default, the file "listing_img_title" of the view "product") via the menu Display>Views and there, load the data, and then generate the links based on the way it's done on the product page.