A couple of years ago, I purchased felt stropping material from SRD. I think it was advertised as rock hard felt, but I am not sure. I do not know the density. Sorry I cannot answer your original question.

What are you trying to accomplish with the CrOx? If your edges are becoming too harsh, you might be doing too many laps. I have found that to be the case with CrOx. Diamond abrasives also have a reputation for leaving a harsh edge if you do too many laps.

Also, are you using a high grade of CrOx? Some CrOx crayons designed for knives and tools tools have mixed abrasives and mixed sizes that might leave a harsh edge on your razor.

You can try other abrasives like CBN. Due to the cubic crystalline shape, they are less likely to produce a harsh edge. I use 0.5, 0.25 and 0.1 micron CBN.

Although somewhat expensive, I have found the glass backed nano-cloth and kangaroo strops sold by CKTG to be excellent substrates for pastes and sprays. They provide a much finer surface than wool felt. Unfortunately, they are currently out of stock.

https://www.chefknivestogo.com/strops.html