The most prevalent rental housing in King of Prussia are townhomes and condos. There are more Townhome rental units. Unfortunately they are a hot commodity and rent fast. Your best bet is to align yourself with a local KoP Realtor who will set up a auto-search for King of Prussia rentals and work his/her local contacts to find something before it's listed. Most of us who work the King of Prussia market know many of the local landlords. Also keep searching Craig's list as well as the other rental sites. I hope this has been of some use.
http://www.trulia.com (Rentals Section)
http://www.zillow.com (Rentals Section)
http://www.realtor.com (Rentals Section)
Between all of those, you will get a very clear picture if you can find what you are looking for. Good luck!