Real Scale Ring mat replacement suggestions?

[Raoul the Great]

I have the Jakks Pacific Raw Real Scale Ring, which has been my go to ring for a long time, so long that the foam underside of the ring mat appears to be disintegrating into a yellow powder. So, does anyone have any suggestions for what I could use to replace it? I see the makers of the “Legends” ring selling replacement mats for theirs, but I don’t know if it would fit the RSR.

[ℍ𝕒𝕣𝕕 𝕋𝕠 𝕂𝕚𝕝𝕝]

Whenever I wanted a new ring mat, I just got one of those $3.99 2XL shirts from a craft store, cut it an inch or so bigger than the ring base, and then pulled it tight and secured it with heavy duty tape to the black ring base. I've been doing it for years to have extra colors for my mat.