We included that information in our annual guide years ago. But tree lots make changes without notice, so it was doing more harm than good. We may get a chance next week to make some calls and add tree types - for example, some (like me!) are fans of Fraser firs, but they're not carried everywhere, so it's helpful to know who has them. Even that kind of info has a short shelf life, once we get a couple weeks in, though.
If you really want to wait for a bargain, usually the last few days of the tree-selling season are what you want to wait for. Christmas is on a Tuesday this year so I would speculate wildly that the preceding Friday is when price-slashing will kick in.