How do I snap a decal to an actor's socket?

I want to use a soft circular texture as shadows from my character’s feet. I can create a decal of a large soft circle and put it at the character’s root position for a general shadow, but I would like to have them track the feet instead.

I can put static meshes on the character sockets but not Decals. I have sockets in the foot area but cannot figure out how to keep the decals on the sockets. Is there any way to do this?