Bleach can be rinsed away with water depending on the composition of the board.

Almost any store that sells general canning / food preservation supplies will have food grade citric acid crystals. If you’re in a part of the world that has Walmart, Target, etc, then those types of places will usually have it. Grocery stores often have it. Sometimes it’s considered a seasonal item and is only stocked during times of the year when people are doing lots of canning (i.e. spring through fall).