RAVCO now makes the AVx4 (Formerly the AV-4 4x4 Amphibious ATV). Here's the link: RAVCO - AVx4
Seems like these amphibious manufacturers are always changing owners, including the AVx4, the Hoot, and recently ODG and Max... Crazy stuff.
$12,500 seems a little steep Though. for $3,500 more, you can get a new Muddox, or you could get an Argo 6x6 for less.