It's great you want to have a go.
Sten Rune and I started with the sporran pattern from the Thompson book
So "you're going to wear the kilt,"
I suggest making a pattern from cornflakes packets it helps to visulize what you are trying for.

We use a good quality Furniture grade leather which is soft and durable.

As regards leather suppliers in the US maybe others can help.

Good luck. I'll look forward to seeing the results