SCA Attire - Historical Clothing and Accessories

I've been meaning to make myself a cloak for a while now, but I don't know where to get the fabric. I've seen some great heavy weight wool cloaks for sale at my local faires, but have never seen that weight fabric at my local stores (only suiting). I'm fine with buying online, but have no idea what to look for in terms of numbers. Does anyone have advice on fiber, weights, and/or places to buy online? 100% wool is best, obviously, but if anyone has any experience with blends, that's okay too.