Any 24 or 26T chainring with a 74 mm 5-bolt circle will work. Granny chainrings don't have the shaped teeth or other shifting enhancements that larger rings do. I have a 26T Sugino chainring on one FC5703 crank and a 26T old SR chainring on another and have used Vuelta and a no-name steel chainring in the past and they all work.