We purchased some RV Sheets from AB Lifestyles on Amazon..... They don't fit the Trump mattress perfect, but contacted AB Lifestyles directly and they will produce king sheets for the thicker mattresses.. They are pricey but well made.
Walter & Donna
2011 CC LB RAM 3500 CTD 6.7L DRW
2013 Cedar Creek 38FL
2014 Days Camping: 35