It was really easy to do, but I thought I would share how I did it. It is not perfect, it is ugly, but it works for me. Feel free to improve on it!
WHAT YOU NEED:
1) a spare patterson reel
2) some epoxy cement
3) a hacksaw or something to cut down the spools
4) a small screwdriver to pop out the ball bearings
5) some needlenose pliers (or something else to trim away some of the spiral on the spool)
6) some sandpaper to smooth down the trimmed down spirals
7) a strip of spare 35mm film to make a 110 test strip (so you do not wreck your negs when we are making this) and a 18mm spacer strip (that is wider than 110 film -- 16mm, so that real 110 film will have some wiggle room).
THIS IS A HACK JOB and is likely not as good as a purpose built spool for developing 110 film. If you want a 100% perfect solution you may want to get one of these purpose-made 110 spools. They exist. There are 16mm stainless steel spools available and also the Yankee Clipper II Tank (which gets mixed reviews). This is a hack job that worked for me and it may work for you. Read through it first and see if it makes sense for you, your mileage may vary, don't hurt yourself doing this, use a roll test roll of 110 film (that does not have any important images on it in case things do not work out), feel free to improve upon it, etc. If you are a perfectionist, you may want to do a better job than i did or buy a commercial product.
Cut one strip of the film to be 16mm wide. This is the width of 110 film. I will call this the "test strip" and will use this to make sure our setup is correct before we actually use the reel, and to practice loading the reel before we really use it. It would be nice if this piece was a foot or so (~30cm), but just make sure it is long enough to simulate loading some film. I suggest this versus using real 110 negatives because if you use real 110 negatives they could get scratched. Plus, you may not have any 110 negatives at this point -- this is kind of the reason we are making this danged thing in the first place ;-)
Cut a second piece of film that is a bit wider, lets say about 18mm wide. We will use this piece to space the reel halves in such a way that when the 110 film is inserted there will be some wiggle room. Make this piece long enough that it can spiral around the reel at least once. A foot (~30cm) should be more than fine.
For both pieces, you should round or notch the corners of the edge of one end of the film to help it slide into the reel.