I'm not sure if this DIY toy has been mentioned in the threads before but I couldn't find any so here goes!
Step 1: Purchase a plastic practice golf ball with holes in a small or medium size. I chose medium just because it seems easier to put things into but still small enough for our babies to have to work for it! I got a pack of 4 coloured balls from Walmart for $5 but I figure you can find them at most stores with a sport section.
-Make sure the holes in the ball are not big enough for your birds head to get stuck in.
-If your bird takes time to warm up to new toys/objects work on getting them introduced to the golf balls at first then continue with next steps
Step 4: Get some string or whatever you'd like to attach to the toy onto the cage (must be safe for your bird to chew on/not get hurt on). I just used the string in the picture below. I just threaded the string between two holes in the ball.