The current interface is clunky and discourages using the Flea Market to sell wolves, especially when there are only 5 listed per page and they don't appear to be in any discernable order. I've personally long stopped listing all but wild wolves for sale because it's difficult to tab through 50+ pages of wolves.
I'd like to suggest that any wolves ineligible for sale not be included in the list of wolves. That means any wolves with companions, apparel, or pregnant/nesting just don't appear in the list when selecting wolves to sell. This would make things significantly easier without having to make any changes to the basic interface/mechanics.