The 2000-2002 Marquis used a Ford H.D. truck surge tank, but I am not sure what the Patriot used. When the surge tank in my 2000 Marquis cracked, Monaco parts gave me the Ford part number so I could buy one at the local Ford dealer.
I would suggest that you call Monaco parts or Beaver Coach Sales parts and either one of them should be able to help you locate a new tank.
Gerald