I see no reason why Bethesda would bother with your email. They have never sold the map as an individual product, and they do not even sell the game itself anymore.
Your best bet is e-bay.
They would bother with the email because along with losing my Morrowind map I also lost maps from Rockstar developed games which Rockstar was more than happy to provide to me, free of charge I might add which is not at all what I even requested. This was mainly because as a distributor Rockstar understand that when I display these posters it is essentially free advertising for their games as both the visual aspect of the map and the conversation that the map sparks about the game.
The fact that the maps are not sold in mass, individual of the game is of no consequence. Also, in my email I very explicitly explained that while I understand the game is no longer in production they might have knowledge of a legitimate distributor who may be able to provide the map at cost. Furthermore as a question of money if I'm offering to buy the map individual of the game that is a mutually beneficial deal for both myself and Bethesda provided they have the map at hand which they very well may. There is no harm in asking and I'm sure Bethesda does not mind either considering the email is a request made out of loyalty to the games they produce.
The prices on Ebay are well over the value of the map and the only ones for sale that aren't bundled with a game (making the prices even more unreasonable) are not the version of the map I am looking for.