Here you go. I can't remember which Ignite figure it came from. It's either the Roman or a Viking. The more I think about it, the more likely it was from a Viking. The Viking mercenary figure also came with a tan leather jerkin but its not as long. It would be easy to paint it black with acrylics tho. Anyway, here is the one I was referring to. You can troll eBay for "ignite leather jerkin" and you may have some luck. I'd sell you mine but its the only one I have.
Alternatively, you could get an Ingite gambeson (which are white) and paint it black. When you use acrylics on fabric, the fabric tends to get stiff. Usually that's not a desired result but in this case it would make the cloth look like leather. The gambeson's are much easier to come by. In fact, I have several if you'd like to go that route (if all else fails).
Best of luck!