The best way to setup your map is to create a system so that each booth can link directly to the payment gateway, and a database to record if the booth has been purchased or not. On the map the booth would show green (or does not have color) for available ones, and a red shade for those which has been purchased. In this case, a new map needs to be customized for the system if you have a different venue, or the booths are setup in different configurations for each exhibitions or events.
You may also consider doing this manually using iMapBuilder software. Import your own vendor layout map into the software, create custom regions for the booths, and provide click links for them to payment gateways. You would need to update the color of these custom regions manually if you have received a pay. This method would work for different booth setup or different venues, as you only need to import a new map and setup the custom regions manually.
Here is a user guide article which would be helpful to setup the map:
http://www.imapbuilder.com/user-guide/define_and_add_your_own_custom_clickable_area.phpYou may let us know if a system approach, or the manual approach would work for your case. The latter one would need some time to setup but the cost can be lower. You can download a trial and see if that works for you.
http://www.imapbuilder.com