Here is the pic of the one I made as a sample for my Sewing Group.
And here is the pattern I used.As you can see, the dimensions are approximately 10" X 10" but it tapers off at the top.
The only other piece is a long rectangle pocket piece which measures twice the width of the bottom of the above piece ( 2 X 10" so 20'' by about 6"".) and two strips of bias tape or self made bias strips to coordinate with the body and pocket pieces.You should have enough to go around the body of the caddy and along the length of the long pocket strip.
Here are the pieces you need to cut out. I use flannelet between the two outer layers of the body of the caddy but you could use interfacing if you prefer.
Here are the steps.
1...Baste together the three layers of the body together. (Sorry no pic ).
2.Fold the long pocket strip in two lengthwise.
8. Press binding to wrong side and stitch in the ditch. Trim away extra fabric close to stitching.
9. Determine where best to add velcro closures and sew in place.
10. Fit caddy to your choice of mug by folding upper half into the mug.
Fasten with velcro closures.
For gift giving maybe you can add a sleep mask which should have a layer of black out drapery lining in between the the two fabric layers because this will make the mask much more effective in keeping out light.
Here is another idea for this type of caddy. A friend gave me this one which has been in my sewing room for years. It has a different design to fit over a tin can with elastic at the bottom. It would need to be designed for a specific size of holder but shouldn't be too hard to draft.