Check out the shops in the DVC resorts ( BW, OKW and VWL) They do have some DVC merchandise, but the selection is limited. When I was at OKW in March, they did have a DVC T-shirt, along with a polo shirt.
When we were at BWV in January, the gift shop had T-shirts, sweatshirts, license plates, and stickers for the car. I'm sure there were others I didn't see, but I know they had these things.