If you're looking to find the fare levels that might meet the conditions you want, FareCompare has a pretty good tool where you can find all the current fares available in the market you are looking at, and will display the rules for each fare level. It's at http://www.farecompare.com/fare-display/index.html, you just type in origin and destination, and can filter by airline once the results come up. THat way, you can see if the fare class with your desireable condition exists, adn then you can give the fare basis code to the agent.