Portland, Lewiston, Bangor

Maine resources:

Wells:

Wilson Store Fixtures (website)
New and used
If you want to avoid Canada, then Maine is a penninsula.

This makes it very expensive to ship to Maine, as any truck that goes to Maine has to turn around and go back.  They can't 'piggy-back' loads, or make other deliveries en route.  They kinda drive double, and kinda charge double.

Check local classifieds like craigslist (website).

Check for local store fixture liquidations in Portland and Lewiston...then just branch your scan out to New Hampshire, then Boston.
If you can't find a closing business, you will hit your first used shelving dealer in Boston.