Need Shop Plugin Recommendations

Hi all, I need some help finding a shop plugin to meet my server's needs. I was planning to use AutoPrice and really liked the idea behind it, but I can't get it working properly and can't get any support besides 'update to Craftbukkit 1.7.10' which isn't happening because all my other plugins are for 1.7.9-R01.

So, what I'm looking for is:

-Server-wide shop for buying and selling
-No chests or signs, would prefer a GUI
-The main thing is I don't want the shop to be able to sell more of an item than it has been sold. So if player A sold the shop 20 iron, when Player B goes to buy, they can't buy more than 20. If none of an item has been sold to the shop, then it is out of stock and can't be bought.
-It would be preferable if the shop automatically adjusted the prices based on supply and demand.

Any suggestions?