Merriams are not terribly hard to come by on your own. The Black Hills in SD or WY, or the Pine Ridge in Nebraska are all three good locations. If your looking for more of a sure thing then I guess an outfitter is the way to go, but a little homework and some time and a Merriams can be had on the cheap. I suspect that is why you aren't getting a lot of response on outfitters.
Eastern Montana is another option, but I haven't looked into it in great detail. For a more scenic hunt with lower odds, you could go after mountains birds in CO or NM.
