I've been searching for a spotted harness and that always takes me to alot of Amish sites. I see alot of collars in my search but can't remember the exact places of the top of my head. Have you tried Yonies? They have alot of driving equipment of all types. The Draft horse suppliers seem to be carrying more mini items, maybe have a look in that direction?
They market collars made by Coblentz Collars out of Millersburg, OH. Hames are both the painted black, steel ones and the stainless steel ones. I have some of both. Prices are very reasonable and depending on where you are, they ship and arrive in 48 hours.