I've seen for years but don't have a machine right now and I've hand sewn all my masks (but I didn't add wire because I didn't need it)

Adding it in after the fact means

1. cutting the fabric, at the nose location, and threading the wire through, anchoring it with hand stitching so it doesn't move and then sewing the openings closed. OR

2. stitching/or fabric glueing the nose wire to the inside of the mask which may touch your skin unless you place a barrier fabric over the wire. Fabric glue is ok but less stable. OR

3. using a fusible web product (that only comes by the yard) that is fusible on one side/fabric on the other to fuse the wire to the inside of the mask. OR

4. using a fusible web tape (that comes in various inch widths) that is fusible on both sides, fuse the wire to the outside of the mask which requires a piece of fabric for the side that goes on your nose to protect your skin. OR....

(easiest) Have you considered looking on Etsy for Disney fabric masks with nose wire?

Those sound like great ideas! Thank you so much!

I wouldn't be surprised if there's not a YouTube video on how to add nose wire to a mask. YouTube is my go-to for any fixes (most recently installing hinges, fixing my rain bird, and how to get rid of wasps)

Or this. Nose pieces. These can go on the outside of the masks.

Amazon has lots of nose clips with self adhesive. This one is probably the cheapest I've seen, if you have Amazon Prime that is. Not particularly pretty tho. I think the suggestion of looking on Etsy for one is the best idea.

Metal Nose Clips

I got some masks from Vera Bradley that did not have wires. It was very easy to open it up and slip in wire and then close!

I use clips that have adhesive. So it can fit without sewing.

The masks I ordered have a sleeve at the top for adding wire. I actually got some fairly stiff electrical wiring, cut to the right length and inserted. The wiring is pliable enough to shape but is stiff enough to hold it's shape as well.

I use the twisty ties like comes on your bread. I have some unused ones. Works great.