anlashokna - there are a couple places you can find equipment in Wisconsin. You can check your local sporting goods store (there is that big Bass Pro Shop in the Gurnee Mills Outlet Mall near the Illinois border). Also Sportsmart, Sports Authority etc. These places will have your cheap sets that may include the mask fins and snorkle for pretty reasonable prices. This gear will be decent, but by no means top of the line. It might also not fit that great - most of the time you can't try it on before you buy it from these places - but at least with buying your own gear, you get gear that only YOU have used, you can practice with it before you go and you can save money over the price of several rentals if you will be using it multiple times on your trip.
My advice for decent gear is to go to a SCUBA store. Check your yellow pages, I can almost guarantee there is one near you. You can get a very good mask that you can try on to make sure it fits for probably $30-60. This mask will last for years (I've had mine for 6 now), will fit great and provide a great snorkling experience. If you wear glasses, you can get the mask fitted with prescription lenses for about $25 over the price of the mask alone.
That price on the Ocean Master Dry Snorkle that 1stNoel linked to from the other snorkling thread on the top pages of this board is a great price - $40 for a great dry snorkle (my brother has that exact one and loves it for snorkling) - you can just order that online. I would not advise ordering a good mask online - you need to see if it fits you first.
Fitting a mask: for those that are buying one and don't have a salesperson to help you, try the sniff test. Place the mask against your face lightly. Make sure you don't have any strands of hair between the silicone of the mask skirt and your skin. Now inhale slightly through your nose. Don't suck in a lot - this will give you a false impresson of a good seal. Just breathe in a bit to create a suction. Now take your hands away - does the mask stay on your face for more than just a second or two? If so, it is probably a good seal. Now look up and down and side to side - does the mask have a good field of vision? You want one with the best field of vision you can find that fits well. Finally, put the mask on with the strap - is it easy to tighten and loosen, is it comfortable?
These above three factors are the big ones you should consider if you are looking to buy a decent mask - Fit, Field of View and Comfort.