I only have a budgie, but I assume all birds would like burls because of how easy they are to shred. Just go out in the woods, preferably with a small handheld saw for thicker branches, and cut burls off of pine trees. Bake them in a oven at 200 degrees for 10 minutes and let them cool, then the birds can have them. My budgie pulls off all the bark within a few days, so be sure to get several. A good size tends to be 2-3 inches long. plus they're free!
This is albie's favorite toy. I cant touch even if he's on the other side of the room playing with something else, he will fly over to tell me off for touching it. He bit my mil for touching it when she was here.