I've been using the NGK Iridium Spark Plug BPR-7EIX and they seem to foul out quick. And I have to get them from a bike shop or on line at $12 a pop. I picked up a set of Champion Power Sport 8902-1 at Walmart for $3 each. They look the same, they have the same type tips and they are also Iridium plugs. I put them in yesterday and the bike ran great with them.
Fouling isn't a symptom of a hot plug, and I can tell you from experience that if your jetting and ignition are halfway decent and you get off the choke when you should, you won't be fouling the BPR-7EIX. I know nothing about the heat range or other characteristics of the Champion plug.
I was skeptical of iridium plugs in older bikes for years until Michael Morse got me to try a pair. The result was faster warmup, more stable idle, and a seat-of-the-pants power gain. I haven't looked back.