I think probiotic foods (i.e. insoluble fiber) are about as good as probiotic ones if you're already good and looking to stay on track. Start slow though, shocking the system with fiber can be problematic.

I am in no way an expert and only have experiments on myself to go off, but I've been experimenting on this particular question for a decade or so my anecdata might be thicker than average.

Probiotics to recover from antibiotics, prebiotics to maintain.