a new dragon to put in her cage would not be a good ideal. it just brings up a whole new slew of potential problems.
there aren't many toys for bearded dragons as they are not lizards that play with toys. adding more climbing surfaces, fake plants, rocks etc to the cage will give them something new to explore as would just rearranging the cage contents. you could also try simple toys to see if the dragon does take an interest...just make sure the toys are dragon safe, too big to swollow, not heavy enough to potentially injure your dragon, etc.
not sure if it would actually be used, but you could always try putting a light rubber ball, big enough so the dragon can't eat but not so huge if it rolls down his back or limbs it won't injury him. those soft spongy balls might be fine, just make sure it can't be bit, as the spongy bits if swollowed could cause problems. not sure if the dragon would have any interest in pushing the ball around or would ignore it like a round rock. hard to say what interests a dragon to play with.
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PHLdyPayne