I got the idea from reading past posts that all the ersatz tin helmets used the 'V' notch type but I looked through the kokarden section and couldn't find a Wurttemberger ~ so you are probably right. I really don't know. I might try contacting others with similar helmets and ask them what they have. Thanks for the heads up - I am learning, just slowly!
So, it looks like I should just be looking for an M91 EM Wurttemburg Kokarde and matching Reich Kokarde for my Ersatz helm.