Get one from UPS instead of the USPS, and it will look like a office suite when you sign up for stuff on the internet.
http://www.theupsstore.com/Pages/index.aspx
UPS P.O Box adress look like this :
Example:
Joe Smith
PMB XXX or # XXX
12345 Somewhere Street
Some City, Some State Some ZIP
So There is still a box number ... :S
Not sure if this matters, but when I purchased a UPS Private Mail Box a few years back I had to send them a scanned copy of my passport. idk if u also need to be US citizen or not, you'd have to ask about that.
The usps offers street addressing on there po boxes to same as the ups.