Kingfisher offers an Iwama-style bokken. Their weapons are excellent (and expensive) in general, but I can't comment on the Iwama specifically.
I've got one and it is very nice. I even was able to fairly easily reshape it to exactly match the shape of my instructors bokken. My instructor says it is not in the Iwama style ...
The (our) dojo gets bokken through California S&P but not the Iwama style one ... hombu style is the 'correct' Iwama style bokken. Drives me crazy trying to get one.