I, too, used the same material as the vest. As for a pattern, I just concocted one from scratch. Long enough to wrap around the ankle, to be secured with Velcro. Some people attach the spat to the boot with glue, thread or Velcro as well. I left mine separated so I could wash them from time to time.
I figure that when I'm out and about in the costume (makes it sound like I'm going shopping in it!) no one's gonna have reference material to compare me to, so as long as it looks authentic, that's good enough. If you're gonna build a display piece that is always compared to screen shots, you'll need to check more thoroughly than me.
After looking at the spats really, really close, I'd say they are made of the exact same fabric as the jumpsuit, not the vest. I'd go as far as saying that they are the exact same color, only the spats are not weathered. Below is a pic from MoM of a spat meeting up with the jumpsuit. Judge for yourself.
For the longest time, I would have agreed with that statement, but after viewing the Chronicles pic of Fett standing on the bridge of the Star Destroyer, I think he may have been wearing them, although they appear to have shifted to the sides of his ankles instead of the front of his boots. This used to happen to mine all the time (safety pinning them to your jumpsuit will remedy this).
Is it possible that the costuming dept. simply forgot to put them on him in a few of the ESB scenes? After all, these are the same guys who put his knee armor on upside down in the Carbon Chamber scenes. :rolleyes
Chris, I included higher rez photo of that pic in my original posts on the spats. That was the only ESB photo I could find that even had a trace of what might be a spat. I could be wrong, but what I think we are seeing is the ankle strapping system, since I cannot find another ESB pic with spats.
I'd agree with you that the last two pictures are definately some type of strap, but the other ones sure look like spats to me, either sideways or backwards. Look at your first picture on his left boot. You can see the closure (i.e. they are on backwards). I think that half the time they put them on, and half the time they left them off, probably because they got tired of having to twist them back to the front (they should have used my safety pin idea).
::Edit:: I'm just throwing this out there. I could be completely wrong.