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HI there, sorry to hear you're having trouble with the tv.
Unfortunately, "case" parts like this are not generally made available for accessory purchase, even for brand new tvs.
As your set is a 2008 model, parts are long discontinued, and no longer available.
While you might get lucky keeping an eye out for one on ebay, craigslist, etc, even there the cost likely won't be practical, you'd probably spend about as much for the part as you would for a whole new tv.
What I would suggest is purchasing a generic wall mount bracket or table/desk mount bracket with a vesa 100 pattern. These are commonly used for computer monitors, and would fit your size tv as well.
You can get a stand type one like this:
Mount-It! Adjustable Tilting Single ... (click for link)
Or for a little bit cheaper you can get a clamp mount type, which would clamp on to the edge of a desk/table/dresser/etc:
Halter Single Pole LCD Monitor Mount... (click for link)