Street sweeper bristles, wiper blade inserts, feeler gauge stock, and many more can be used for bargain material. If you want quality and can afford it, I'd recommend high carbon spring steel. It is great to work with something that you don't have to tear the rust off of or worry about uneven temper on. It'll require more sophisticated tools (to a degree), but it really is quite good for picks. There was another thread with more idea, specific brands, and links to vendors:
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