Well, personally, I shamelessly use the amazing art available at dundjinni.com. Some of their stuff truly is exceptional (you can find my finished maps here if you are curious to see some items in context).


Alternatively, I suppose that you could take a nicely detailed picture showing the symbols that you want and lift them from it and save them as your own brush. I am pretty sure Gimp allows you to do so, although I have only done it once a long time ago, so my memorw may not be accurate, and I'd expect Photoshop to be no different if that's what you use.