I'm not familiar with southern Wisconsin, (other than the fact that people always say how beautiful it is there) but if you live anywhere near a big city, your best bet is to ask in the local groups section of this forum where people get their plants.

I've bought plants from both aquariumplants.com and liveaquaria.com. They both provide decent specimens and you can call either for advice. One cool thing about liveaquaria is that it is a division of Dr's Foster & Smith. If anything goes wrong with your order and you need a credit, your credit is good for anything they sell - fish, plants, supplies - even other pet supplies. One not-so-cool thing about liveaquaria is that shipping charges for live fish will stop your heart as they will only ship FedEx overnight. Shipping charges for plants isn't as bad, though.

Aquabid and eBay will definitely be the lowest price, just be sure to check out the sellers first as quality is all over the map.