Fabric glue - I used Fabri-Tac by Beacon
Jeans you don't want (or that have huge holes in the knees even though they are really nice jeans)
I wanted to use a really heavy fabric for the chaps and vest so they would hang like real leather. luckily the craft store had two large fabric remnants of white vinyl. Nice.
I searched the Internet for Jessie pics and Jessie costumes to find ones that were close to the character. I used this inspiration pic to get a feel for what the chaps should look like>>
Then I just started cutting. I pinned one chap to the pair of pants I was going to donate to this costume, refined the shape a little more, and then cut another one for the other leg.
It is very helpful to have a toddler help you practice being "scary" while you ponder upon the shape of the chaps.
Then using tracing paper, or tissue paper, I cut out some cow print spots that resembled the cow spots on the actual Jessie character's pants.
Finally I sewed the black pipping around the outside edge, and added a few white frills off either chap.
Then, well, this is the part I hadn't thought of till it was upon me. I had to hand sew each chap onto my jeans. I don't know what else I was thinking, but I really thought this step would be easier. It wasn't bad, I'm just not very talented at sewing so it was slow.
Honestly the vest is exactly the same process just no black piping.
Using a vest we already had, I just traced the outlines onto the vinyl, cut it out, and sewed the ends together. Poof. Vest!