looking for a very firm mattress

hi there,i have purchased an extra firm mattress from Paul Simon called "MERLOT" unfortunately is not in the market ,so i was wondering if you could help me ,basically is an extra firm or hard mattress im looking for ,because i have a back pain only this type of mattress i need , just firm will be still soft by experience,so if you have the MERLOT mattress that was branded silent night or something similar ,i will really appreciate it.
kind Regards