Reader in search of bookmark for spiral books

Reader Sharon Y emailed me recently asking if I've ever seen a bookmark that fits onto the spiral binding of planners or notebooks. I haven't so I thought I'd put the question out to you all.  This would be a very useful thing if it exists!

The thing about these types of bookmarks is that the attachment has to match the size of the spiral, so it's difficult to have a standard size for the bookmarks.

Has anyone seen these for purchase anywhere? Please post a comment with any ideas or recommendations! Thank you!