Places in the US where you might be able to find a used "button box" (i.e., Cajun accordion) is at -
The Button Box in Massachusetts http://www.buttonbox.com

The House of Musical Traditions in Maryland http://www.hmtrad.com.
Those are both on the east coast.

In Michigan there is Elderly Instruments (a great music store)
http://www.elderly.com.   Occasionally Elderly has used accordions in stock.

Castiglione Accordions in Michigan http://www.castiglioneaccordions.com but I don't think they ever have any real bargains.

Mark Savoy - Cheapest Accordions are around $1200US & takes 6-12 weeks to build.   www.savoymusiccenter.com.

Larry Miller - makes the Bon Tee brand of Cajun Accordions. 
www.leebenoit.com/boncajun/accordions.htm.

Junior Martin - Accordion builder has a good reputation
www.koukous.com/martins.htm

All of the above information courtesy of
Garry Kaluzny - http://acs.madonna.edu/~kaluzny/cajun

Washboards-- Home of the RU Rhythm Boards, Ray Nutter, West Virginia.   www.freewebs.com/rurhythmboard

SOME CAJUN PLACES TO EAT AND DANCE IN LOUISIANA…
For the Music, the Food  the Dancing, and the love of good times..

Mulate's, the original Cajun Restaurant  in Breaux Bridge has live Cajun music every night of the week.

Mulate's, near the Riverwalk, in New Orleans, has live Cajun music ever night.

Michaul's Live Cajun Music and Restaurant, 840 St. Charles Ave, new Orleans.
www.michauls.com

Prejean's, Award winning Cajun cuisine and live Cajun music, Lafayette. La.
www.prejeans.com

Randol's Restaurant , live Cajun music and dance hall, Lafayette.
www.randols.com

Café Des Amis. Breaux Bridge.  Zydeco Music on Saturday mornings.
www.cafedesamis.com

VENUES

Downtown Alive, venue for outdoor Cajun and Zydeco concerts, Lafayette.
www.downtownalive.org

Grant Street Dancehall, Lafayette. Music venue and Zydeco dance classes. 
www.grantstreetdancehall.com

Blue Moon Saloon, Lafayette.   Music and accommodation. 
www.bluemoonhostel.com

Bayou Boudin and Cracklin, Bed & Breakfast Cabins, Breaux Bridge.
Rocky and Lisa Sonnier.    www.bayoucabins.com

"As an Honorary Cajun, you are entitled to celebrate on any occasion and to
always pass a good time.  You are required to love Louisiana's food and music and share its "Joie de Vivre"  (Joy of Life) with the world…"