DAvid, Here is a set of sling swivels. $13 and free shipping.--------budsgunshop.com/catalog/product_info.php/products_id/44429/u+mike%27s+mag+cap%2fswivel+set+m500+12g

David, yes you can for th models that don't come with the sling swivels. gggaz.com/mossberg-shockwave-quick-detach-rear-sling-attachment.html

the Mossberg site shows it with the sling swivels installed I suggest contacting Mossberg and seeing if this is correct or if you can get the factory swivels mossberg.com/product/590-shockwave-6-shot-50659/ contact Mossberg at Tel: (203) 230-5300 | 8:00am-4:30pm Eastern
Fax: (203) 230-5420 or mossberg.com/contact-us/