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I have Gore-Tex gear, US Army ECWCS (Extended Cold Weather Clothing System) and British MVP (what the Brits call their Gore-Tex).
I have Gen I ECWCS in US Woodland (full set pants and jacket) and a jacket in 3 color desert. I have a British MVP jacket in desert.
I also bought an aftermarket jacket from Otte Gear in CADPAT which is really nice equipment but very expensive stuff.
The ECWCS stuff can be had from surplus stores or eBay and the prices vary. You kinda have to watch and bid what you want to pay on the chance you might get it or not. It is my experience the Desert stuff goes cheaper than Woodland.

If you do some research on ECWCS you will find it is intended to go over the cold weather gear (with liners) and I have worn it this way but it also works fine on it's own over a t-shirt or fleece.

I camp a lot as well as airsoft so I could justify the expense as some of these items can get a bit pricey, but I'm not going to tell you about eBay I'm sure you already know how that works. If you are making a trip to the US I'm sure many surplus places would have it.

Oh year forgot to mention, Gore-Tex is awesome for keeping you dry, but it is noisy. You will make a "swish" noise every time you move so you probably won't get any knife kills.