I personally know two JLL imitators, and both are excellent. One is Jason D. Williams, originally from El Dorado, AR, where I used to live many years ago. He did the music for the movie. He even looks like Jerry Lee. You would have trouble telling them apart by listening. He probably plays better than JLL.
The other is Brandy Roberts, has spent most of his life doing it small time, but worked in Branson, MO for a number of years. He is selling used cars in Shreveport last I heard, playing occasional shows locally or regionally. He's really good too, but neither is the REAL thing.
Brandy is a really great person, and differs from JLL in that respect. I've lost touch personally with Jason, but he was dang near as wild as Jerry when he was younger. Not sure if it was an act or real.
http://www.rockinjasondwilliams.com/
http://www.brandyroberts.com/

Jason in action: https://www.youtube.com/watch?list=PL8E2757C9D09352E6&v=K13bHgEukok