While you can buy such an adapter it will not function. Here's why. In the world of USB we have clients, hosts and USB2GO (see google as I would be duplicating the web if I wrote more.)
Since the E2 and LT 40 are both clients they will not function over the USB.
My E2 did have bluetooth and I used that to connect to bluetooth GPS devices.
I am trying to connect my Tungsten E2 with my Earthmate LT-40 gps. They both have male USB. Is it possible to purchase a female to female usb adapter to connect these two? If so which is the brand I should use? Thank you!!!