I am also confused why you don't want to order online but if you are looking for cheap ones, most cobblers have them. Otherwise AE and BB has decent cedar ones for $20-$25 and if you want to blow the budget try Hanger Project.
Most places that have split toe cedar shoe trees seem to have the same size chart. My shoe size is between 7.5 and 8.5, really depending on the brand of shoe. This is borderline territory for the Nordstrom (and many others) between small and medium.
Any idea which one I should get? Will the small be enough to keep the shoe properly supported? Will a medium fit in my shoes?
The regular Nordstrom (non-rack) will carry them during their sales. Most AE and BB stores also have some. But I'm also curious why you don't want to purchase online? Usually they are cheaper and wider selection online...