Hello and welcome to WI when you arrive!
Some options might be as follows:
Waukesha Sports Cards - https://www.waukeshasportscards.com/ They have cards but are probably a bit more into autographs and sports memorabilia
AJ's Collectables - https://www.ajcollectable.com/. They have more of a full selection of cards and plenty of boxes to sort through. Also a large selection of sports bobbleheads and some other memorabilia
Brew Town Trading - https://brewtowntrading.com/. They also have a full selection of cards, plenty of boxes to sort through and other memorabilia.
Jeff's Sports Cards - https://www.jeffssports.com/. They also have a full selection of cards, supplies, etc.
Brew Town and AJ's are pretty close to each other (a few miles). Jeff's sports is a bit further north but on the same West side of town/suburbs. Waukesha Sports is out toward Brookfield way.
Those might be some of the best bets that I am familiar with. Unrelated to cards be sure to check out a Kopp's Custard for a cone when in Brookfield or just down the road from Brew Town Trading.
Enjoy the trip!
