Authenic Hogwarts Robe Patterns?

[Grant Levy]

I'm looking for an authentic pattern for an adult Hogwarts' school
robe.

I'm not happy with the Butterick or Simplicity patterns that
are currently available.

I don't want to have to buy one of the robes I've seen for sale
in the store (and online) and then have to rework it (the hood's not
deep enough, for one thing).
 
Anybody got any suggestions?

Thanks,
Grant Levy
Costa Mesa,
Orange County, CA