Unfortunately, this part is not available for purchase. Typically, case parts such as this are not stocked in any quantity, even for current production models. Hisense is one of the lowest quality brands out there, and offers virtually zero support for their products in terms of parts availability.
For older or discontinued models, it is nearly impossible to find them, and no dealer or part source has them in stock. Even when they can be found, the parts tend to be very expensive (sometimes several hundred $).
If you want the factory original base, you can watch for on ebay, craigslist, etc, or check with local tv repair shops who may parting out a defective tv.
Other than that, your best option will be a generic/universal base, or to wall mount the tv. Here is an example: http://amzn.to/1jibnBH or http://amzn.to/1jibux9
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