Adding some width to western chaps is easier than you think.
Take the zipper half without the pull off the chaps with a seam ripper. Then sew super wide elastic to that side of the chaps. Make sure you turn under the elastic at each short end and sew a hem first.
Then sew the zipper half that you took off to the elastic. See how much extra width it adds?
Basic essentials plus a leather needle and quilting thread for your sewing machine.
Here's what it will look like before you let the fringe fall!