There are a couple of bait places around, but not many. April Sound Marina is on the water and has shiners, but I think that's about it. There's a place called Benny's on 1097 (not on the water and their prices aren't great) and another place in New Waverly called The Minnow Bucket.
I haven't fished for cats recently, but usually you can catch them on the 1097 bridge or on baited holes on standing timber around the Scott's Ridge area. If it's windy, stay off the main lake, it can get pretty brutal out there.
The Fish Lake Conroe Facebook page is also a good place to find out where they're catching them right now.