Alternative to graphisomorphism that respects edge weights but works on adjacency matrix rather than digraph object?

I am checking whether many thousands of weighted, directed graphs are isomorphic. Right now I'm doing it with isisomorphic() which works very well but requires that I use the digraph() object for comparison. This is the only place in my code where I actually need the object; everywhere else the adjacency matrix suffices. The code would speed up by a significant amount if I could use graphisomorphism() for this, but that function ignores edge weights. Any alternative?