If possible, after your initial research, go to an early music festival or exhibition to purchase your flute. This is the best way to try out many flutes by many makers all at once, and they’ll often have discounts going. I purchased by flute from Martin Wenner while he was at the Greenwich Early Music Festival. I’ve been incredibly pleased with its consistency, and several well-known baroque musicians, including Rachel Brown, own Wenner instruments.
Another good place to start your instrument search is The Early Music Shop, who have showrooms in Saltaire (West Yorkshire) and London and carry flutes by a variety of makers.
The following is not an exhaustive list, but rather a collection of makers with fine reputations, whose instruments are played by professionals in the field.Wenner Flöten: