If you go to Walters Bridge, you can stop at Douglas Lake Market there on 25E just before the bridge, they have minnows but they are a little higher than most.
If your going to Swanns, just down the road towards Dandridge is 'Bucks & Bass' tackle shop, thats where we buy all of our stuff. Swanns also sells minnows, but you get the best bang for your buck at Bucks and Bass.