I had a request for this part from someone on eBay. Thankfully I bought some internal latches from France for a F-601, F65 and F75 just to have as references. This was a perfect opportunity to model the latch and make one.
The N4004 makes its real easy to test since it is a piece of cake to change on that camera. Just take the bottom plate off and the two screws on the side plate and remove the latch. The spring likes to go to high orbit so make sure to put your hand over it when you remove the old one.