Baby toys can be so expensive and sometimes it's the simple things that keeps baby happy.
Thread some interesting buttons onto a length of flexible wire, leaving a small space so the buttons can slide around to make the rattling sound.
Tuck the end of the wire in and tie a pretty, bright ribbon around it several times so that no sharp edges stick out. Ensure you fasten it securely to avoid buttons sliding out and ending up in baby's mouth.
The brighter the buttons and ribbons you choose the better.