Hi g1981c,
If It was me … I would probably add a stretch knit cotton mattress protector (not another topper) such as the ones mentioned here on top of the wool mattress protector. This could be washed and would be like an extra sheet. I personally wouldn’t use a down alternative (polyester) topper over a wool topper which would lose much of the benefits of sleeping on wool but of course each person may have different preferences or prefer different combinations.
Phoenix