Gary,
Aerus told me the same thing. The fact of the matter is that these were discontinued about 10 years ago, give or take. Aerus gave me the part number, but when I went and entered it into their inventory system, it didn't even come up as a valid part number. If it is a currently available/stocked inventory, the system will list a price and show that it is active. They know darn well that unless old stock is found hidden in some place, these are no longer available. By telling us that they are on back order, it was a way for them to avoid an embarrassing situation and admitting they were wrong in the first place.