amazon.com has this Olee Sleep 10 inch Aquarius Memory Foam Mattress – Full for $191.73 shipped.

• 3 inch 8 ILD soft memory foam supports body with soft power
• 3 Inch 25 ILD HD foam prevents defection of memory foam
• 3 inch I Gel disperses temperature accumulation to maintain a constant mattress temperature.
• Dimensions: 75″ L x 54″ W x 10″ H