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are you referring to the Xperia X housing or are you referring to the LCD and digitizer?
To the best of my knowledge, I don't believe Sony sell spare parts directly to the consumer.
Doing a quick search online the frames being sold from third parties don't seem that expensive, though I cannot guarantee their authenticity.
What is the issue with your phone? You may wish to contact your Local support team to arrange an authorised repair.
As this is a local matter I recommend you get in touch with your Local support team to discuss it.