I wasn’t able to find one, which I found surprising given how it is used so successfully in non healing wounds described in that paper. But copper oxide is pretty easy to source–I picked it up on Amazon. Added maybe a tablespoon to a swat sized jar of chlorhex? Try on small area just in case your horse objects, but it does seem to be helping mine. (Do note that copper SULPHATE is in a few proud flesh preps. Different action, don’t think that’s appropriate for this need. Everything I was able to find about wound healing described copper oxide.)
I’ve been SO pleased with layering chlorhex and udder balm (it’s the Dr Naylor’s one, but I’ve got to think anything really emollient will do the trick.) Give it a try, hopefully it works just as well for you!!