Hi Bill
The US did develop the 'Mark 15 Mod.1 Demolition Unit' as a bomb sight destroyer. As far as I can tell it was only issued to the USN, so you probably never saw one.
It was an 18" cylinder 51/2" in diametre packed with magnesium and an oxidiser which acted like a blow torch, directed at the sight.This might be confused with a thermite device. It may have been effective, but sounds rather dangerous and might well have brought down the entire aircraft. Having said that the .45 calibre solution seems to ignore the dangers of richocheing bullets, at least to the fellow tasked with firing the weapon.
The first intact Norden sight which the Germans definitely got a good look at was that on board a B-24 flying from Tobruk to Oran which ran low on fuel, landing in Spanish Morocco. Franco's officials allowed the Germans to examine the aircraft and all its contents before permitting it to continue its flight.This was on February 25/26 1942.
The US was very paranoid about the security of the Norden sight, but in reality it would have been difficult for the Germans to copy (had they wished to). Furthermore, they would have been obliged to change their air power doctrine, training systems and even the aircraft its industries were producing to make use of the sight.
I have seen US documents which substitute all sorts of odd words for 'bombsight'. A list I made included siding, latent, telescope, mickey, dusty and talon.
Cheers
Steve