How about allowing players to put one or two items up for sale that can be accessed by viewing their character? You can have a tab that shows the items that the player is currently selling when someone views their character info. An icon can be added next to the player's name so signify when they have something for sale on their bazaar. I'm sure slots can be purchased similar to what's being done for the CS.
I also suggest that this be tax-free and there are no other fees. This could also make trades less of a risk from people changing the item or price at the last minute.
This is just a rough idea and I'm sure it can be expanded upon.
