They're discontinued. I ordered one from a site that still had it for sale, and got a call the next day saying the part has been discontinued. I had to buy a used one. Got it from the Corral.net classifieds. There are also two different styles of GT-40s (intake cover wise). Mine has the 4 holes closer together, while the later versions had them farther apart. I got one that was farther apart but it still worked. Only two bolts lined up, but that's ok. Good luck buddy.
Nick