Had a similar problem with my old Zenfone...
Usually best chances are ebay and AliExpress.. but depending on how new your model is, it might be costly. And adding insult to injury: It's a real pain to do that yourself (hairdryer and all).
EOD: I gave up those glued crap phones altogether and went for fairphone instead. And I don't regret that choice
PS: I don't know if that applies already but wasn't there some EU directive demanding manufacturers to provide spare parts? Perhaps the Asus people themselves will help you?