Amber from Nakedly Knitting has pointed out a good yarn to use for this coat (here), Noro’s silk garden chunky, color 02. This is a beautiful yarn, and I am sure that the jacket she makes out of it will be georgeous, but whether it is mimicking the coat in the Golden Compass depends on what is the most important thing about the design to you.
If the general colour and shape are most important then this is a good substitute, and you can find garter stitch coat from a book or magazine and make a very good facsimile. But to me the most important thing about this jacket is the texture and specific colours. I love the way the colours slightly clash: the brown and the purple don’t really go with the red (see here), but they come together to make it sing. Noro yarns are beautiful, but they are too harmonious to make this coat the way I envision it. The hint of green in it tones down the red (here); purple makes the red brighter.
I also really like the effect of the areas worked in slightly different thicknesses. It gives the jacket brilliant texture and makes it unusual. I don’t want to make this coat, because I don’t think I can replicate the parts that make it most exciting to me.
On the other hand, the construction is completely unimportant to me. If I were making the coat, I would completely change the construction for various reasons, which I will expound on later.