Would anyone have a sewing pattern for a rekkel or kapoteh?

I have been looking for a pattern for cutting out a rekkel/kapoteh? More specifically the style that ends about an inch above the back of the knees, with one vertical central cut.
I would not turn down any other pattern, though!

Mostly, I am looking for something that I can download, or is laid out on a grid of known size so that it can be copied easily.

Thanks so much!