Build a Model of K9 MKII from Doctor Who

I would like a Model built of K9 for my daughter based on dave everett plans. Once the model is built I can put in the electronics and update as I go. I was thinking it could be built with high impact polystyrene for when we take it to conventions and that it can be as close to metallic gray as the tv show prop as possible. I appreciate the help my daughter loves the tv show and would love to surprise her with this.