I was gonna send a PM, but I think this might be something others would like so...
I'm reluctant, but excited to talk about a guitar strap. They can be just as personal as the instrument. I'm an electric bass player and the instrument is heavy. So, I usually look for a wider strap. A 3 1/2" to 4" is about the right width. The problem with ordering a custom strap is that most leather workers make things that are intended to be stiff like holsters and belts. A guitar strap is not that way. It needs to be soft and supple. Otherwise it will chafe as it is used.
Even so, I'm willing to take a chance if the price is right. Because it will be "one off", I can send you the length and it can be made out of one piece. I'm not looking for a lot of tooling, but one symbol like this cross would be great(it wouldn't be this large):