Probably not what you're looking for but we bought a 50mm memory foam topper for our R&R, for a sheet we bought a plain quilt cover and altered the width to fit. In use it just fits nicely, might be ideal for the SCA mattress? Very useful on the R&R too, when making the bed just fold it back, pillows, quilt and all to the back of the van and put the seat up; at night just pull the seat down and roll out the bedding, job done