I'd guess it's hard for people who know carpet, or are willing to help you search, to make suggestions without more info. Pictures of your home and especially the area surrounding the stairway would be helpful.

I have a couple of wool rugs from Masland. Very high quality and very thick and not be what you would want for stairs. They should have something else suitable though.

Stark has great offerings.

Stanton or Stark but both can be pricey.

I had a gorgeous Stanton wool carpet made for our dining room. It is so nice and feels wonderful underfoot! They had so much to choose from...traditional to more contemporary.

every hear of Caravan wool rugs?