John Steed's Bowlers

[Mycroft]

I beleve he said he got them via his taylor, along with his suits, but he seems like a James Lock and Co. type of guy.

 

[Matt Deckard]

There is an episode where, I think it might have been in the New Avengers, but a scene where one agent has to prove he knows Steed to another agent by asking the agent who made Steed's Bowlers.

The answer was James Lock.

In the episode you can tell it's a Lock bowler (or coke hat) by how the the bowler hat's rough finish.

You'll see in earlier episodes... Emma Peal Era that the bowler has a smooth finish. In one of these Emma Peal era episodes there is a scene where Steed's bowler is lowered onto a miniaturized man and you get a close up of a Herbert Johnson Lining.

So I'd say earlier years it was Herbert Johnson, and later James Lock.