material for making and modifying figures

as a matter of fact, yes it is

I use Magic Scuplt exclusively. I love it.

Here's a basic step by step on how I use it.

http://www.promodelmaker.com/photo.html

Sculpey is available in the States, as is Super Sculpey. I know several who use it and they say that Super Sculpey is a far superior product for figure work. It requires baking however. That's the only drawback, though that is also a good thing as far as working time goes. You can heat cure epoxies like Magic Sculpt (I do all the time) but it will cure on it's own over a few hours.

Is that the moggle of Final Fantasy fame?

Sculpey is a common product, but I don't know if it's availabelhere (think so, but not sure). then there's Miliput. Carftec in East Windsor has this and War iN Pieces in West Hartford shoul, too.

I don't have any direct answers, but here are some resources to look at.

Sculpting Figures & Sculpting Products @ Michigan Toy Soldier Co.
Green Stuff: The Basics @ Games Workshop
Miniature Wargaming: Sculpting
Sculptor.Org - A Comprehensive Resource for Sculptors