trout man
Dont over look Appalachian trails bait shop. Just a few hundred yards east on 422 from 528. On the right just past the giant chicken!
This is probably the closest. It really depends where you are coming from, for most convenient though. Who knows which ones have minnows at this time of the year. Probably best to call first.
O'Donnell's as noted above. Always seems to keep stocked & nice guy too. Kind of a long trip from there to 528 area though, but not too far off of 79.
Roger's Rifle and Reel on Mt. Union. Kind of a PIA to get from his shop to 528 Launch (probably the same time from O'Donnell's, but maybe 3-4 miles straight line...). He is the closest by far to the North Shore spots. North Shore Dr. stops at the marina, if it kept going, he would be the closest to 528 Launch. Nice guy and keeps a good selection of wiper plugs at good prices.
There is a shop about a mile off of the 79, Slippery Rock exit, across from the Dairy Queen towards SR. If you are coming from that direction and know the back roads, it isn't far to the 528 area. Not sure of the name or Winter hours. I have only seen the signs passing the place, and never stopped.
Used to be a place in Zelienople, but not sure if it is still open. He was an older gent, about 10 years ago when I was last there.