I have a P. O. Box! When asked for street address and it's says no P.O. Box I put the street address of the post office where my Po. Box is! With the PO box number listed too. I was told I could do this by the one of the employees at Post Office. I do this with packages and some mail(if allowed by that company). If it will fit in box they will put it there. If it's a package, and will not fit in my box, I can go to the counter and get it. Hope this helps!

For example
200 Old Hendersonville Hwy. #676
Brevard, NC 28712