what material can I use that hardens like plastic and mouldable like clay?

Question

we have to create this sort of casing for the small motor for our gadget. Its for our investigatory project. :)

Answer 1

Use 'Bondo` (auto collision repair plastic).
It has about a 20Min. working time, can be
finish filed / sanded when set.
Needs no baking.
(Do use gloves to keep it off your hands.)

Answer 2

Sculpey is like clay and can be baked to hardness. Or any other kind of polymer clay.