I've heard of no other Windstar rear axle sources. If you're looking for better pricing, a trip through wrecking yards in salt-free states is probably the best bet at this point in the game, close to 15 years since the last Windstar rolled off the assembly line.
I successfully performed the dancing instrument cluster gauge needle fix (and it's still working fine over a year later). My report here:
http://www.automotiveforums.com/vbul....php?t=1147951