Anyone know where I can get those screw in metal caps for the DR5 and DG2?

I have done a pretty exhaustive search and have come up with zip nada.

Scott, do you have a photo of what you're looking for? I'm at a loss to even know what to search for. What does the cap do?

This is an eyepiece adapter for the DG-2, but I have no idea if it's what you mean. https://www.bhphotovideo.com/c/product/520428-REG/Nikon_4784_DK_18_Eyepiece_Adapter_for.html

This is a DR-3 but that cap will fit if I remove the DK-17 adapter. Same goes for the DG-2

I spent some time searching but also came up empty. However, I'm not sure if Nikon made anything to cover the back end of it - based that by looking at the pics for new ones as well as what's supposed to come in the box as new. You might want to contact Nikon and ask.