They're from John Deere.  I can't remember exactly, but they're in the $200 range when I bought the tractor.  With steel prices right now, who know's how much they are.  The do have a little curve at the end to match the inside of the bucket, so I don't know if they'll work with your bucket.  I would suggest going to your local JD dealer and order just one, and see if it will work.  Then you can just order as many as you want.  I have 7 across a 6' bucket.  JD wanted me to put 9, but I thought that would make it harder to pick up brush.
J.