To reduce bulk, I was only planning on suggesting that he was wearing an entire suit of chainmail under his surcoat, and only having it sewn on where it would show - on the sleeves, and along the bottom showing under his surcoat. But I didn't have enough of the stainless steel chainmail to make an entire 'skirt' without piecing lots of parts together, plus it would be ridiculously heavy, so I opted to use aluminum chainmail for the bottom instead. It's a lot lighter, and easier to work with, plus if I used it with the wrong side out, it would look reasonably similar.
The aluminum chainmail was from fancy clutch purses I'd collected from Value Village over the years. I've found it in several different colours and sizes. But the 'silver' aluminum was too 'silver' compared to the stainless steel chainmail, so I decided to stain it some with diluted brown paint.