I was browsing the clearance section at Books for Half the other day and came upon several books of a very healthy thickness. They weren't books I was interested in reading, but I knew that Charli would enjoy them.
Better yet -- they were either half a dollar or a dollar each! You can't buy much of a bird toy for that little these days.
Charli has approved of these purchases. I only have three left, but I'm confident Books for Half will be able to supply many more.