Do they make bed skirts long enough to cover bed risers?

I think you can find 20" drops in basic colors... white and ecru for sure. Maybe not in store but online. Since most skirts you see are 15" drop, this would be a little better. Otherwise, think custom, because you can specify almost any drop and style (gathered, box pleat, tailored). And then there's my favorite trick... DUCT TAPE! I duct taped lengths of fabric that I hemmed onto the back of a standard skirt to be sort of an "under skirt" in a contrasting color. It actually looked great, since it was a simple gathered skirt.