I got this almost 3 years ago and love it
DynastyMattress New Cool Breeze 12-Inch Gel Memory Foam Mattress https://www.amazon.com/dp/B00828APY8/ref=cm_sw_r_cp_api_i_KUwQCb8Z5FSEV
I got a memory foam mattress from Amazon. I made sure in the comments it was firm. It was like flip pin' concrete at first,and I kept waiting for it to break in. It's been almost two years and I've barely broken it in at all. We caved and got a thin pillow top mattress pad. Best decision, and best sleep of my life. I'm trying to learn to sleep on my back, I've been a tummy sleeper my whole life with a cocked pelvis and my arm out of its socket under my head. So weird that it's comfy, but I've slept like that for as long as I remember. This combo is the most comfortable I've ever slept on and because it's comfortable in all the positions I've tried I am able to stay on my back which is what everyone is recommending for avoiding serious back issues.
DynastyMattress New Cool Breeze 12-Inch Gel Memory Foam Mattress-King Size-CAL King Size https://www.amazon.com/dp/B00828APY8/ref=cm_sw_r_cp_awd_M-0xwbCD4P1ZM
And this is the mattress topper we have: Hospitology Heavenly Microfiber Goose Down Alternative Overstuffed Mattress Pad / Topper, 72-Inch by 84-Inch, California King
https://www.amazon.com/dp/B00EFBD0MU/ref=cm_sw_r_cp_awd_Eb1xwbV4HFQM4