Substitutions:
Instead of char siu, try chicken meat, chicken gizzards and livers (my mom was fond of these), fresh or dried shrimp, or omit the meat entirely.
Dried radishes may be difficult to locate and there is no adequate substitute. Leaving it out will eliminate one of the textural elements of the dish, but it'll be delicious nonetheless.
Experiment with additional ingredients: cut corn, chives, onions, cashews, bell peppers.