Billings, Missoula, Great Falls

Montana doesn't have an active store fixture dealer, nor a huge metropolis which make finding a closing business easy.  Without a little luck, you will likey end up getting a shipment from out of state.

You will want to check craigslist (website) for liquidations in all local areas, Billings; Butte, Missoula and Great Falls.

Bordering states and cities are worth checking for store fixture liquidations, but you are surrounded by sparcely populated regions.

Your nearest dealers will be in Portland and Seattle, and these dealers are active.  Portland and Seattle are also your best chance at finding a closing retailer
Try these nearby states:

Minnesota

Washington

Oregon