you might look into organic coconut oil.
i know people have had success with this type of thing with their dogs and cats. i don't know for sure, but it seems like it would help a hamster too. you might try mixing a little in his food, see if he eats it. but you can also rub it on his skin/fur. coconut oil is generally good for skin/hair issues, although like i said, i haven't heard anything specifically about using it on such little animals. but it's a good bet, probably worth trying. wishing you and your pet the best!