Feel free to add your own findings or discussions in this thread whether it's a glass screen protector, PET screen protector or those wet flexible type.
Found a few glass screen protector on the market, most being non full coverage due to the 2.5D curved edge on the xperia X performance. I don't have X performance ATM, but should have it on the 29th, so I can't actually test them out yet, but these protector should work for both the X and X performance.
Got this locally from china at a cost about USD 0.30 each, doesn't cover the full glass area due to the curved edges, but being cheap to buy, there is no reason not to try them out.
Purchased these 3 days ago, and had them delivered today, these being full coverage and at excellent quality, the cost is also very expensive, this one shown in the photo's that I purchased being the cheapest of the 4 types on offer, the full screen protector underneath has adhesive, color available is metalic glittered/gloss finished.
Normal clear version PET edge with 0.21mm thick glass available to match all 4 color variation.
Super hard clear version PET edge with 0.21mm thick glass available in gray and white only.
Private version PET edge with 0.21mm thick glass available in gray and white only.
Mirror/non reflective version (not 100% sure) PET edge with 0.21mm thick glass available in gray and white only
price starts from approximate USD 27.50- USD 38 for different versions.
Seen these available in china, 100% glass, just like the ones for samsung S7 or the LG G5, only has double side adhesive on the edge, the active part has no adhesive, cost approximate USD 5- USD 15, the prices will slowly drop with time.
Another one is PET and Glass, all clear, from china, cost approximate USD 10
One's from china can be purchased from www.taobao.cn or www.aliexpress.com
The other one can be purchased from www.amazon.co.jp or www.yahoo.co.jp
No direct link will be given, so you have to search those sites for them, and yes you can purchase them, but not directly if you don't live in those countries, but there are ways to purchase them and will incure additional cost.