Learn the tools and you can make one yourself.. or if there's already one out for another Q3 engine game you may be able to convert it... I must say you're the first person I've seen request one though.. ; )
Ofcourse a ferret model can be made, if they can make an Ysalamiri model for usage in JO MP, than a ferret should be no problem. Altough as a playable model you'd be in trouble lol. Everyone would stomp on you ^_^"