Mattress topper for backache in the mornings?

A few months ago I started having lower back pain when I got up in the morning, which is completely relieved after sitting in a recliner with a heating pad against my lower back for an hour or so.
I have posted here a few times, and finally decided to replace our 9-year-old latex mattress. We bought one from Ikea which was quite firm. Unfortunately it didn’t help with my morning back pain at all. Perhaps it’s because it’s too firm.
So now we’re thinking of buying a topper to see if that will help. We’re thinking a good quality latex, 3" thick.
My questions are-

Do you think this will likely make a difference?
What brand would you recommend?
Is Amazon a good place to buy? (Been happy with them in the past).

Thanks for anyone’s advice, or comments.

HH

Would this likely help with my morning back pain?

What brands would you all recommend?

Any other suggestions most welcome…