Mike:
I was thinking of the brake wheel from hte modern boxcar set whic hI have on hand, and which is the same size as the Eric brass ones. These are slightly wider than the nook in hte carbody into which they must fit.
However, your comment about "the smallest" prompted me to check their website and I see that they have a set of just brake wheels, to whic hyou are obviously referring. I will have to find a photo of that set and check it out.
Shamoo:
I wondered if the MTL Z brake wheels were available separately - that would be about the right size as I need to drop about 25% in diameter.
Thanks for your help,
Tim