I don't know anyone who sells mud minnows in this area. But get a minnow trap at Walmart and place a can of cat food or old hot dogs in for bait. Then drop it in any shallow tidal creek. Once you catch some, put them in a bucket with about 1 to 2 inches of water in it. Too much water and they will die.
Cwest, You'll have your best luck on trapping at dead low tide. Find a tidal pool when the water is out and put your trap in that. Leave for thirty minutes if that long and check it. I use the little cans of cat food, tender liver and chicken with good luck. I just run a wire around the can in the trap and twist it down around the can to hold it stable in the trap.