raffia is the artsy thing you can get at craft stores that looks sort of like string made out of straw. it comes in different dyed colors but i would get the natural color one. I just hang a few strands in the cage to gnaw on, and you can hang some toys from it too. it is very appealing to keets.
as far as biting - sometimes my keet would get SOOO excited if he was eating brocolli out of my hands that he would start biting the fleshy part of my finger tips really HARD - it killed. But after wobbling him a few times he stopped and I don't think he's done it for at least a year now if not longer.