In the Sammons Preston Catalog, there are dishes available that will help keep warm food warm and they are called "Keep-a-Temp Dish and Bowl".  They range in price from $12.75 to $13.25.   They may be worth the investment!  Sammon Preston's toll free number is 1-800-323-5547.  They have a catalog that is available for free.
 
Sincerely,
 
Bonnie Cunningham
NPF