Dry macaroni noodles are a favorite of my GCC. Obviously they don't last long, but they are cheap and fun to crunch into bits. Small pieces of balsa are also fun.
Most toys actually sold as foot toys for parrots are meant for larger birds, and, even if your GCC loves the toy, their foot will get tired and they will drop the toy within a few minutes.
Now, if you are just looking for small bottom-of-cage toys, and not toys your bird has to actually hold in his foot, then there are a lot of toy barbells and balls that can be lots of fun. Just beware of toy balls with jingle-type bells in them - those can catch claws so they should be for supervised play only.