There are a number of tankers around. There is a KC-10 at
http://www.avsim.com/ffg. There is a K/F/A-18F at
http://www.flightsim.com. Look for the file name fa-18f.zip. There are a number of KC-135s here. Just search for them. Also, there is an KA-6 at
http://www.avsim.com. If there is something specific you are looking for, let me know.
P.S. The KC-10 and KC-135s do not have moving booms.