It depends on the rest of your repertoire, but I'm guessing you want to stick with lines where your Knight goes to f3.  It's probably good not to stray too far from your old line so that you still know what to do against Black's early deviations and things, also.

I recommend the Classical with 7.Be3 instead of 7.0-0.  A lot of themes should be fairly similar to the Petrosian, but it's sharper and I think you'll have more winning chances.  Probably more theory as well, but less theory than in the Classical Main Line.  It's good enough to be your main repertoire choice against the KID forever (or until you get bored).

If you want more of a change, you might try the Averbakh, which is a line with a very high pedigree that I like a lot.  It's probably one of the least popular lines below Master level, so that should help you out as well.  That Bishop on g5 really annoys KID players (I also play 6.Bg5 in the Saemisch) and White's plans are very flexible.  However, it's a very sophisticated opening: White's King could castle to either side or stay in the center, sometimes he throws his Kingside pawns down the board (not in an effort to mate Black, but to lock up the Kingside), etc.  I think it demands a high level of positional understanding to play well.