I had an order for the filigree butterfly stoma cover...and after discussing the length, I decided to make it up with a doubled aqua satin cord, with a chain extender to adjust the length if needed.
Here's a picture...these are custom made of course. This example would be $15.
This is the link to my website, showing the stoma covers that are currently available. You will find a section called Stoma Covers in the left hand column.