"I am strongly considering using lacing to bring the sides in a bit."
That's really the only way to do it. Just use a small drill bit. No drill needed. You can put the bit in a set of vise-grips. Make two (or more) holes in each skirt. Be careful not to make them too close to the bottom of the skirt for fear of it tearing. Then remove one of the laces from those black dress shoes you never wear. Lace it in the four holes. Pull it tight and make a simple bow in the middle. It can be easier with a helper to keep it tight while you secure the lace.