Um if you wanna make it a particular shape , use plastic. Add an L_C_D_ screen , add a scroll wheel , that'll be fine.
Yeah.
Or make it just push-buttons. Basically plastic gives you the b biggest variety of of options. Maybe not the nicest feel. Or not much originality really.
So the ru wait the rubbery  we can shape it however we want ? Or the rubbery we cannot ?