need help with a GREP statement

I'm trying to select just the x

舌ぽう (舌鋒x) ぜっぽう (sharp) tongue
じょう舌 (饒x舌) じょうぜつ garrulity, loquacity 

Its always in parentheses. So I want to LookBehind for a left parenthesis then zero or more characters, and LookAhead for zero or more character followed by a parenthesis.

I thought this would work, but it doesn't: (?<=\(.?)x(?=.?\))

This one will select all the text between the parentheses, but I only want the x: (?<=\().?x.?(?=\))

I also tried this (not sure if you can have two lookbehinds...but it didn't work:

(?<=\()(?<=.?)x(?=.?)(?=\))

I'm out of ideas.