Callie checked out a couple of different styles online and decided that the best option seemed to be either a "ring sling"
I read lots of different DIY instructions for each type and found a great tutorial for it on Pinterest.
directions I used. Before shopping for fabric, I looked through my rather large stash and found one that was perfect. I bought this fabric several years ago with Callie in mind---I planned to make a skirt, but never got around to it. (these photos were all taken with an iPhone in pretty horrendous lighting situations) And yes, there are loose threads on the fabric---as you've probably guessed, there are loose threads all over my house!
Once it was completed, we couldn't wait to give it a try. Great fit and he seems to be quite secure in there.