Aghh right thats what it is, Can you get these for the Nikon D40?
The battery grip is a simple plastic case/cartridge to holdmultiple batteries for the camera, anybody with some basic electronic background knows well it's just some wiring to the 3 contacts Positive Negative and Ground direct current, the problem is how to mold the unit to fit the camera unless you have someone who is ready to put upfront a sum of money to makethe casting and send it for mass production and make a profit.
Yes, there are some small companies in the business to do so outside the US where the labor cost is low. They have the battery grip for the D70 and D50, the D40 is new, if they don't have it now they'll soon have it, who doesn't want to make money onsuch asimple unit? Caution, any battery grip not made by your camera will void the warranty contract.