I agree that a naturally tanned leather product would be your best bet at preventing snags, and covering other requirements in your list. I think these clothing items might be a bit pricey to invest in, but the investment would likely be worth it as the item would be able to serve it's purpose for many years. But cool in the summer? Not.
I have looked at prices for clothing that fits this bill, all natural, locally made, etc. and they aren't as cheap as what is available en masse. It's BECAUSE of the specifics of things like local and organic that raise the price. "Specialty" clothing isn't inexpensive but it does exist.
Have you tried thrift stores? The shopping process takes more time in these, but you can find wonderful rewards. Often "on the cheap" as it were.
Shy of growing your own, spinning the threads or yarn, butchering the animal you raised and tanning yourself, then making the garments needed, I'm not sure there is an easier way to find them, and being sure they fit. However, I'm finding that 100% wool can be warm or cool. Linen and silk wick moisture away from the skin.
I hope you will keep us apprised of the rest of this story as you journey along it!