OK, so I know this is going to sound crazy but hear me out...
Samurai banner flags players can wear on their backs that signify what services they can offer. Other players click on the flag to see prices/message.
3.bp.blogspot.com/_Hv-1mLTN...
As in: A food flag for players who want to act as food merchants - click on the flag to see prices.
Or
A herb flag for players selling herb
Or
A no-no flag for players selling no no!