This is not rocket surgery. Foam is foam, a bass is a bass, so just try different kinds of things. For muting people have used foam, fabric woven through the strings, and even things like hair scrunchies wrapped over the strings around the first fret.
If it helps, the original foam between the bridge cover and the strings on my 1963 P-bass is essentially the same foam used for dense weatherstripping applications. I still have that foam in storage.
"The best way to tell a lie is to tell the right amount of the truth, and then shut up." Robert A. Heinlein