Product review (4 stars): Gap Cap for Stovetops by Miles Kimball
I would have given five stars, however as reported by other purchasers, unless the counter and stove are the exact same height it does not lay flat.  The four stars is because they look expensive and do keep most things from falling between the gap.  This, however, is because the level difference is very slight.  Highly recommend if the level between counter and stovetop are level.