I know this is a little off base, but I
have to suggest them!
Ella's Lead is my addiction. So just know if you buy one of their collars, you'll get a collection! Rebecca is the owner and she's incredibly nice, personable, and just wonderful. When I got my cat back I explained the situation and she made a discounted collar just for her. (I can send pics if you'd like!) They use real leather, mainly latigo leather, that lasts years upon years. (Some customers have had a collar for 5 years still "new" looking.) It's worth the investment, IMO. She also makes collars of all sizes, she's easily been able to make Great Dane collars and would be able to do a TM no problems. She makes leather collars 3" thick for dogs like ours! Again, I know it's off base, but they're my "go to" for collars.
I'm not sure if she makes rolled leather, but it's worth an email. She will have you measure their neck sizes and will make the holes according to that.
Here's the website;
http://www.ellaslead.com/