Nikon D5000 LCD viewfinder?

I'm looking to invest in a video setup for my Nikon D5000, I do a lot of wildlife photography and want to start doing some wildlife videography. I use a Sigma 100-300mm f4 and will be buying a new tripod, gimbal or ball head (not sure yet), 1.4x teleconverter. I also want to get an LCD viewfinder but can't find any for the 2.7" screen size of the Nikon D5000.

Do you know of any companies that make an LCD viewfinder for 2.7" screens?
Otherwise, can you mount an LCD viewfinder for a 3" screen on a 2.7" screen?

The loupe (LCD viewfinder) I bought just had rubber bands to connect it to a camera, so it would attach to a smaller screen. Look around your screen. Is there anything that would be blocked by a loupe?