If you want to make your own, here are the steps...
Step 1: Use a sharp, serrated knife (like the bread knife seen here) to cut a cork into six equal pieces. I like slicing through the middle first, and then cutting each half into thirds.
Step 2: Use an old nail file (or fine sandpaper would work, too) to smooth the cork pieces. I did both sides to make them all the same texture.
Step 3: Using a fine-tipped Sharpie in both red and green, alternate colors to spell MERRY. I added a sprig of holly for my last charm. The font you see is of my own creation, but others would look equally nice.
Another view.
Step 4: I bought tiny eye-hooks online (but they can also be purchased at Home Depot). These, purchased on Amazon, are 3/16". The wine glass charm rings were also an online buy. These are 35 x 40mm, but I wish I had gone with a slightly smaller diameter, as these are just a little too large.
Step 5: You'll need to apply gentle pressure to screw the eye-hook into the cork. I centered my hooks above each letter. Thread the ring through the eye-hook and voila! You've got your finished product!
Overall, I like the way they turned out. We even used my sister and brother-in-law's set at our holiday gatherings! My one mistake: I didn't make US a set. I'll have to rectify that next time.