That fabric wasn't "off the shelf" so I dont think you'll get one as they were done by hand. I think you'd probably just need to create a template from the stills. You could even just draw on the swirls (using taylors chalk or something similar), and then stitch over them
Note:
Some of the swirls were sewn, some were drawn, and some were a mix of both, so to get an authentic look you may want to try the same.
Both of my reference libraries (DH and OotP) have some nice reference pics, but I'd head to the OotP one first as there are some shots like these in there (these are a bit blury as they've from screengrabs, but there are some high res ones too):
Showing the sewing being done (and you can just make out the trace pattern)
Showing some "weathered" versions:
Swirls on some leatherwork:
Lucius' OotP (Death Eater Outfit) Tunic Pattern:
This one is quite dark, but what it shows nicely is how each Death Eater's swirls and fabric vary:
They all have the swirls, but the swirls themselves seem to have random size, direction, shape, compression (i.e. some are like very loosely sprung springs, and other seem more tightly wound), different colour threads, different amounts of weathering, etc... and yet the beauty is, they're all still obviously so related. Very nicely done.
I dont think you'd get this kind of effect if you used a regimented template/printed patterned fabric, and that's why they look so organic I think.
Check out the "Costume drama" documentary as that's where those screengrabs are from. It's a really great insight into the work of the costume team!
