Michigan Holly Ilex verticillata (Common winterberry) is a beautiful plant during the fall and winter, and as you can see from this distribution map, it is quite prevalent throughout the state. You say you have used it before, but I want to make sure you are aware of this caveat found on its NPIN profile page:
Warning: All Ilex species may be somewhat toxic if ingested. Sensitivity to a toxin varies with a person’s age, weight, physical condition, and individual susceptibility. Children are most vulnerable because of their curiosity and small size. Toxicity can vary in a plant according to season, the plant’s different parts, and its stage of growth; and plants can absorb toxic substances, such as herbicides, pesticides, and pollutants from the water, air, and soil.
Bloom time is from April to July, and the berries persist through fall into winter. The woods should be resplendent with them about now. When you say looked for them and foud nothing, does this mean no Holly berries or no Holly plants? For information about this problem closer to home, you might try this link to the Michigan Botanical Society, which is the Native Plant Society of Michigan.
For information about wreath making check out this article in our Step by Step Guide .
There is a very well illustrated article on native holly plants in the Winter 2012 issue of Wildflower, The Magazine of the Lady Bird Johnson Wildflower Center ; vol. 29, no 3. Members of the Wildflower Center receive a subscrition to the magazine as a benefit of membership.