Nippon Denso do an iridium plug (IX 24 B) with a 0.4mm centre electrode (NGK is 0.6mm) comes at a price though, £15ish, I have one on order.
I have to admit, when I went in to the garage to measure a spare NGK I sat on KLX for a minute.
KLX and LS plugs are the same fitment.

Clive W  

To change the plug on KLX you need to take the side panels and rad scoops off, this allows the seat and tank to come off, then with a long box spanner you can get at the plug.

Clive W