In Massachusetts, I would start with the Massachusetts Flower Growers Association. They have a membership directory that list the different Massachusetts wholesale poinsettia growers.

You might try Schaefer Greenhouses in Montgomery Illinois. Although this Montgomery IL florist is in northern Illinois, I believe they can service places in central Illinois for this type of fundraiser.

My go to source FGmarket has a couple of new York vendors that carry wreaths: Fantastic Crafts Inc and Decorative Traditions, Inc.
For the poinsettias you might try W. D. Henry & Sons in Eden New York or contact the New York Nursery Landscape Association.

I check my favorite wholesale blooming plant resource FGmarket and found a nursery called Baucom’s Nursery> Another great place to look for poinsettias in South Carolina would be through the South Carolina Nursery & Landscape Association. The director should be able to help you find a member who grows and sells poinsettias wholesale locally.

I’m not sure where you are in Tennessee but I know a grower in Arkansas Parks Brothers Farm, Inc. that has a Plants For Profits Fundraiser program. I know that they ship to some places in the following states Arkansas (all), Tennessee, Missouri, Kansas, Oklahoma, Texas, Louisiana, Mississippi, Nebraska and Iowa. They might ship be able to ship poinsettias in to your area. Although this time of year they may be sold out. Usually you need to secure the poinsettias a couple months in advance. If they do have plants they are a great company to work with - Clay, Jason and Dwight are all very helpful.

Another place you could look is the Tennessee Nurserymen’s Association. The TNAL director should be able to tell which of their members growers poinsettias and if they have a fundraising program.