Got this from Amazon. Have a memory foam mattress in the s&b and love it, this was substantially cheaper. It's also an expanded queen (6" wider) and fit perfectly in my Winny. Will see how it holds up.
LUCID 10 Inch Gel Memory Foam Mattress - Dual-Layered - CertiPUR-US Certified - 25-Year Warranty - Olympic Queen
https://www.amazon.com/dp/B0088YUXLG..._Ly4AlirnMmnVr