Here's a place I buy from that raises jumbo Wisconsin. They are the same size. No other differences in bobwhites that I am aware of besides size and mutations like tn red. WI and Butler the same, GA giants a bit smaller and standards are the smallest.
Very good people, very good prices and very healthy stock.
By the middle of june they'll be available everywhere.
It costs a boat load of money to raise bobs under artificial light commercially and the demand in the off season isn't sufficient for most suppliers to want to run lights, heat, and water in a building all winter, when they could just toss all the birds into a flight pen for a few months and re-pair them when mating season starts.