I did a search for this a few weeks ago and I could not find it. Now I'm looking for something else and I find it anyways...

I was looking for something similar. I wanted to have BOTH the Buy Now and More Info link and I did it by modifying the modules/MY_TEMPLATE/product_listing.php file. I only have one attribute on all the products and it's optional so no need for the client to have to see the individual product page.

For those still looking to be able to do this:
Make a copy of includes/modules/product_listing.php and place it in includes/modules/YOUR_TEMPLATE/product_listing.php

Find (Line 115):
Code:
$lc_button = '<a href="' . zen_href_link(zen_get_info_page($listing->fields['products_id']), 'cPath=' . (($_GET['manufacturers_id'] > 0 and $_GET['filter_id']) > 0 ?  zen_get_generated_category_path_rev($_GET['filter_id']) : ($_GET['cPath'] > 0 ? $_GET['cPath'] : zen_get_generated_category_path_rev($listing->fields['master_categories_id']))) . '&products_id=' . $listing->fields['products_id']) . '">' . MORE_INFO_TEXT . '</a>';
Replace with:
Code:
$lc_button = '<a href="' . zen_href_link($_GET['main_page'], zen_get_all_get_params(array('action')) . 'action=buy_now&products_id=' . $listing->fields['products_id']) . '">' . zen_image_button(BUTTON_IMAGE_BUY_NOW, BUTTON_BUY_NOW_ALT, 'class="listingBuyNowButton"') . '</a><br />' . '<a href="' . zen_href_link(zen_get_info_page($listing->fields['products_id']), 'cPath=' . (($_GET['manufacturers_id'] > 0 and $_GET['filter_id']) > 0 ?  zen_get_generated_category_path_rev($_GET['filter_id']) : ($_GET['cPath'] > 0 ? $_GET['cPath'] : zen_get_generated_category_path_rev($listing->fields['master_categories_id']))) . '&products_id=' . $listing->fields['products_id']) . '">' . MORE_INFO_TEXT . '</a>';
Do the same with Line 133:
Code:
$lc_button = '<a href="' . zen_href_link($_GET['main_page'], zen_get_all_get_params(array('action')) . 'action=buy_now&products_id=' . $listing->fields['products_id']) . '">' . zen_image_button(BUTTON_IMAGE_BUY_NOW, BUTTON_BUY_NOW_ALT, 'class="listingBuyNowButton"') . '</a>';
Replace with the same code in the middle.

This is what mines look like
Products with Atts: connecticutvalleybiological.com/advanced-placement-biology-advanced-placement-by-neosci-c-65_75.html

Without Atts: connecticutvalleybiological.com/test-cat-test-subcat-c-67_68.html