Here's a curiosity from the November 4, 1946 Rochester Democrat and Chronicle. You can read for yourself, but it's the mention of "the flashlight with which Houdini exposed many mediums" that made me light up.
William Larsen Sr. was Bess Houdini's lawyer and did have a fair amount of Houdini artifacts, so this certainly sounds legit. Unfortunately, I don't know who "Karlin" was. But if the flashlight was around in 1946 and understood to be Houdini's, is there a chance it still survives today? What an illuminating piece of Houdini history that would be!
UPDATE: Our great friend Joe Fox from the Magic Castle library provides the identity of Karlin the Magician. Thanks Joe!
UPDATE 2: The flashlight survives and you can see it here: This is Houdini's seance flashlight!