You are exactly right - they are more difficult to find precisely because their duller colors make them less popular and, therefore, LFSs find it more profitable to stock males exclusively. It's a great shame realy...
This is the excuse they give us anyway.
I don't believe it at all.
Since when do people buy fish only for color? It's more natural to buy pairs and most people do just that when they are available. Females aren't dull either. They are a beautiful silvery color.
The lfs don't carry them because the distributors they get them from don't have them. The distributors don't have them because they can't get them from the breeders. Why can't they get them from the breeders, you might ask? I think it's because they have line bred these unnaturally colored fish and don't want them to be bred by hobbyists. The only way to control that is to keep all the females.
I've looked and looked and only once found female dwarf gouramis of this type. The sad part is that the males still sell, and the lfs now stock them almost exclusively. It's almost impossible to find natural colored dwarf gouramis anymore, and they were every bit as lovely as the ones available today.
If I can't get females, I won't get the males either. If more people did the same, perhaps we would find them more readily available.