M* sells wool charms offering a nice selection of colors and textures at a reasonable price (use their search engine by keying in "wool". Also, Weeks Dye Works has the most beautiful hand-dyed colors with a luxurious hand but a bit more costly (Weeks Dye Works | retailer | over dyed | fiber). I've purchased 100% wool from Joann's (less expensive if you can use a coupon) then hand-dyed to my preference.

I have also purchased gently-worn 100% wool clothing, which I felted and hand-dyed. My resource books advise to stay away from men's jacket, outer-wear coats, and blankets simply because of the thickness but personally I think it all depends on your project's requirements or the look you are trying to achieve. A tip from my experience when buying used clothing is to check for fused interfacing especially in jackets/skirts. If there is a lot of fused interfacing, walk-away from it; if there are large sections without
interfacing, it is worth buying.

Very important tip when purchasing used wool clothing: immediately wash the used garments as soon as you walk into your home or seal completely until you are able to launder because I've heard stories of moth infestations!