Way back when I used to run the delis for Copp's Corporation in Wisconsin and have been hooked on Usinger's sausages ever since. Can only recommend that you order them from the web site. Tain't cheap, but if you buy a bunch of stuff at once, the FedX charges are tolerable. http://www.usinger.com/
Other than that, I've seen Usinger cooked brats at Trader Joe's, but I'd much prefer to buy the fresh and do the cooking myself.