I'm sure you'll get nursery recommendations from folks in the Metro area. You can also check out the seasonal garden centers that spring up in the parking lots at Wal-mart, Home Depot, Lowes, Menard's, etc. if price is a major consideration.

There will be someone who cringes at the big box suggestion (and will write that you "get what you pay for, they don't take care of things, their staff is incompetent", the whole nine yards). In fairness, you can pay big bucks for a specimen from a reputable company that has been mishandled and dies on you, too.

Just keep in mind that arborvitae is deer candy if you're in an area where deer are present. I lost 6 of them over this winter - chewed clear through to the stem from the ground up as high as deer can stand on two hind legs. No way they can recover from that! They're being replaced with assorted Spruce which has proven to be resistant so far.

I am sure you could find them in which ever Twin Cities quadrant you live in. Do plant them in the spring or early summer, not late summer or fall. Trees that big are almost always dug in the field, rather than grown in pots. You will see them in burlapped balls of soil, or burlapped balls put in pots (maybe with soil to cover) for merchandising. So if they are tipped in the pot, it's just because they wern't put in straight, and is not a concern. Since they are recently dug, most of the root system has been severed. With trees that large, they need most of the growing season to recover before winter sets in.

The Smaragd arborvitae (a.k.a. Emerald or Emerald Green) is much narrower than Nigra, and a more refined tree. Nigra is wider, and more natural looking.

If money is a concern, go to the big box stores, and where ever you buy, be clear about any guarantees that come with. While 1 year is a standard, some small nurseries differ. And always, save your receipts!