I've never seen them for sale anywhere. I got mine years ago from a native fish collector. I only have one male left in my 153 gallon pond but he is super gorgeous! I only had a few and never found any offspring. If you want to get some you can either get a fishing or collection permit and go catch them, trade with a native fish collector, or go to a native fish or regular fish club where they might trade some. My page on SRD is at
http://www.fishpondinfo.com/dace.htm and includes links to the native fish clubs where you can meet and trade fish.