I know of a young<?> lady located in the UK who makes collars (and harnesses and leads and ...) who would probably be able to give you some good help / suggestions.
You can see what she does at indi-dog and I've chosen one of her harness pages so you can see the type of thing she does and the prices she charges.
_________________
“Properly trained, a man can be dog’s best friend.”
Corey Ford .