From Elemental Lords of Porphyra

Adamantine Bear
Aura moderate transmutation; CL 11th; Weight 1 lb.
Slot none; Price 10,000 gp
A rare version of a figurine of wondrous power, this barely-tooled lump of meteoric iron only vaguely represents a bear. When the command word is spoken, it transforms into a fully-grown polar bear that can be commanded by the user as a mount and ally. The adamantine bear can be used once per month, for a period of no more than 12 hours.
Requirements Craft Wondrous Item, animate objects; Cost 5,000 gp