I Am Trying To Find Out Where I Can Buy

I am trying to find out where I can buy a lesser known antibiotic prescribed by my doctor for long term on going UTI. The drug is Monurol 3 g oral powder for reconstitution. There seems to be much information regarding the drug on line but not who supplies it.
I think I need to find a large company with large distribution centers some where even though I live in CA it really does not matter where it comes from.