I kinda think most of us make our own patterns when it comes to this (just like determining our favorite lengths of ribbon to sew bows).
Me- I took graph paper and drew out what I wanted. I played with the ratios to determine the height of the bodice/height of whole bow holder, and width. I wanted it mathematically balanced- it just looks more pleasing to the eye (I think).
I sew mine. I think it's more sturdy that way. All the tulle is sewn. All the ribbon is sewn. Everything is machine stitched for durabilty. The embellishments are glued on.
Here's a picture of two of mine. I'm sorry it's not focused more on the bow holders.