Hi! We have a 1999 H3-45 and went to pursue a new mattress that would need to be custom made. Upon investigating multiple sites with prices anywhere from $1200-$2600 for a custom made king size,I was fortunate enough to find with the help of Ben Cummings from Coach Worx's a man who made me a custom size king for $500.00. It fits perfectly,it is made of latex foam and will last 20 years! Let us know if anyone is interested and the name of the business is AJ's furniture and Bedding in Largo,Fl.