I didn't see any $500 Visas at my Kroger in IL, but they have 8 million of the mastercards of this type:
http://romsdeals.com/wp-content/uplo...0321295569.jpg
They had some Visas of smaller amounts on the rack. If you've never been to a Kroger family store look around - mine has at least 3 separate gift card racks in addition to some random cards at the checkouts.