Hi mindys,
There are too many unknowns and variables involved to make specific topper suggestions because softness and firmness can be subjective and relative to different body types, sleeping positions, and individual perceptions as well as the firmness/softness of the mattress underneath it which will also affect how soft or firm your mattress/topper combination feels.
The only way to know whether any mattress/topper combination will work well for you with any certainty will be based on your own personal experience so the return/exchange policy of the store you are dealing with will become a more important part of any purchase choice for a topper that you can’t test in person on your mattress before you buy it.
Having said that … post #2 here and the topper guidelines it links to can help you use your sleeping experience as a reference point and guideline for choosing the type, thickness, and firmness for a topper that has the least possible risk and the best chance for success.
Phoenix