Here's a thought. In NH, there is a system whereby landowners can receive a tax break by putting their land into a "current use" land tax classification. There are 2 tiers, and the one that gives the higher tax break requires that the land is open to the public for recreation.

If you go to a town hall, you can request to see the tax records. If you ask, there may be a fast way to ID the properties in that classification. Those properties are open to hunting. That doesn't mean an owner can't refuse you, if for instance he already allows a bunch of hunters, but that should be a way to find land for hunting.

It may surprise you to see how many of those lands are posted "No Hunting".