Just an update to my earlier comment (post #24), I was able to find a website for the Brentwood Mattress and was able to sent them a message and ask about a RV Short King.
www.brentwoodhome.com and their email is
support@brentwoodhome.com. I did get a reply and they do not have the Short Kind 72x75 ... so I'll have to keep looking or perhaps cut the regular RV king (72x80) down to size. Cutting (as Al Fiallos indicates) kind of makes me nervous on getting a straight cut and what to do with the extra mattress cover. Thanks jeeplj8 for starting this thread ...