We removed the carpet from our stairs and ordered hardwood that matched our other floors to be installed on the 40” wide treads.  We did not want to paint the risers because we were concerned paint would chip and not stand up.  We found this Lucida MaxCore (piano white) luxury vinyl plank on Wayfair.  Each plank was 7.25” high and fit in the riser perfectly.  The installer only needed to cut off 8” at one end for the proper length for each tread.  He added some glue to the backing.  The plank is a flat white and looks so much better than a painted riser would have.  Any scuff marks wipe off easily with a damp cloth.  Very durable and looks fabulous.