they made a model for him in 5th edition... but its prery rare, I think I saw one on eBay one or twice....
If you check the GW website theyve just put the 5th edition model of Oxyotl up for advance order along with the old metal skink command groups. Hope this helps
Here is the GW link for Oxayotl... http://www.games-workshop.com/gws/catalog/productDetail.jsp?catId=cat440004a&prodId=prod900131a