I am seeking to build this item and looking to sell it in the market and it looks like this patent is expired. Is that true? Can I purchase the patent for this item? The patent number is US 20050243651 A1
The "patent" number you have cited - US2005/0243651 is not the number of an issued patent. It is a patent application publication number. As it happens, that application did end up producing an issued patent US 7,029,170. Google patents shows this in the upper right hand corner under "also published as" when you go to the US2005/0243651 publication. The issued patent subsequently expired due to non-payment of maintenance fees on Jun 8, 2010. That information is shown by google patents also.
Since there is no one with rights to this expired patent, there is no one to buy rights from.