Nunatak will make it custom for you, Katabatic doesn't, if that helps. Jan will work with you to get you exactly what you want. Their Instagram page is well worth following.
I just emailed Katabatic about this very thing on wide vs regular for the flex line. I was told if my circumference around shoulders measures more than 52" at widest part than I need a wide.
I've never owned a quilt and i'm torn between a Katabatic or getting the Stone Glacier Chilkoot 15 mummy bag. Both use pertex and Allied treated down, so quality and construction I feel is very similar. The quilt is much cheaper so that is a plus. This will come down to if I actually like a quilt or not.