What do you considered odd size? Have you tried asking Redding and Wilson for what you're looking for?
Speedy Gonzalez has a full set of carbide neck bushings, in .0005" increments from .256" to .261". [source: 6mmBr.com]. You might call him at Trinidad State Junior College, 600 Prospect, Trinidad, CO 81082, 1-800-621-TSJC and ask him where he got his.
Also, Sinclair International carries Redding bushings of .185 through .368 in .001" increments.
And, on page 52 of their 2009-B catalog they list and show pictures of Carbide Neck Sizing Bushings for the 6PPC in 1/2 thousandths [.0005" increments] for $38.50 each.