It sounds like you're looking for the Denver Mattress Perfect Fit RV Mattress Protector # 656561 for a bunk-sized bed. This will fit over the top of mattresses up to 12" tall (thick) and has an adjustable drawstring so it fits snug on your mattress.
We also have a variety of other mattress accessories that I'm linking for you to filter through. view full answer...
I spoke with my contact at Stromberg Carlson and unfortunately the Acme Jack Nut 911-10 is not available as a replacement part. The only option is to replace the landing gear leg. I am not sure which leg needs to be replaced or which landing gear you have but I have attached the replacement legs for the Stromberg Carlson landing gear systems for your reference.
The Replacement Lead Leg for Stromberg Carlson Landing Gear - 33-1/2" is part # LG-177202
The Replacement Follow Leg for Stromberg... view full answer...