Best place to find Superman the Animated Series?
 

Hopefully B&M. I would like to get all the Seasons at once, but if I can't then that'd be fine as well.

Thanks!

Obviously dependent on whether you're a member, but I got all of the seasons at BJ's for 12.99 each. Costco may have a similar deal.

BJ's?
Also, do you think Sam's Club may have the same deals as Costco (because they're owned by the same company?)

Since when is Costco owned by the same company as Sam's Club (Walmart)?

Costco merged with Price Club in 1993, not Sam's Club. That may have been the source of confusion for the OP. And to answer the OP's question, I think you'll find it very difficult to find all three volumes in one place. I live in the Louisville metro area, and I can only think of a couple places I've even still seen the Superman animated series: Barnes & Noble, Best Buy, Borders and Circuit City. I don't believe any of the locations of those stores that I frequent have all three volumes. I just checked, and Best Buy, for instance, shows Vol. 2 not available at all in the Louisville stores. Granted, they may just not have the requisite 3 on hand to show as available, but I think they're genuinely not in stock.

If price is an issue, I always suggest looking for things like this at either a local used media store, or a comic book shop. They rarely conduct sales online, meaning your only real way of knowing what they have is to call (or, better still, show up), but they're also a lot likelier to actually have them on hand--and for less than the retail stores.

In my experience, most of those places have a pretty thorough quality control screening process for items they take, and especially at a comic book shop, the previous owner was probably a collector who took great care of it in the first place. Plus, you can look at the package and all the discs prior to paying (dude, alliteration!), meaning you don't have to worry about being dissatisfied with the condition.

Happy hunting!