Magento – get product small image url not working with resize

$item should be an instance of Mage_Catalog_Model_Product so you should be able to get the image url using the catalog image helper:

$imageUrl = (string)Mage::helper('catalog/image')->init($item, 'image');

[EDIT]
So your code should look like this (only the section that should display the image)

<div class="image_product">
    <a href="<?php echo $item->getProductUrl(); ?>">
       <img src="<?php echo Mage::helper('catalog/image')->init($item, 'image')/*->resize(200, 200)*/; ?>" alt="<?php echo $item->getName();?>" />
    </a>
</div>

If you want the image at a specific size, just uncomment the resize method and change the width and height.

You can take a look at this post at my answer or Frank's.

Maybe one of the ways posted there could help you.

Images returning as placeholders - custom product collection