There is no model of Nidoking from any game, so your only option would be a fan-made model from a 3d modeling program.
D: that sucks, nido king is beast
Someone in Aafyre's thread said they were making a vertex of him on Bowser. Not sure if they actually started or not though.
I attempted one on Bowser a while ago but it wouldn't patch out correctly so I gave up pretty early on.
Nidoking is my favorite Pokemon so it's that much worse :/