Wool army blankets are often sold for a couple of dollars each. That is about as cheap as you can find wool commercially.
I have a Capote made from a blanket I bought for that purpose. Mine is blue with black hash marks. It would cut wind and be warmer with a liner in it. Most of the suppliers carry patterns but I can't say off-hand how big they come in sizes.
When I made my own Elk Skin pants, I used a pair of pants that were heading to the trash as my pattern, and simply added more material where it was needed for the different style of pants. You would do the same thing with any other pattern for a shirt, or coat, etc.
Suggestion: Before cutting on wool, first use an old sheet and cut your Pattern out on it. Sew it together enough to make sure it fits where it needs to. Only when that cheap test pattern works, do you then transfer it to the wool and begin cutting. :hatsoff: