Here's a better look at Varavon's latest Loupe Viewfinder. This one has a 180 degree flip up loupe that will provide you shade from the sun, even when you don't need a magnifier. The lens is glass and has a diopter to adjust for vision imperfections. Solid build with metal mounting brackets that can be positioned to fit a variety of cameras. The bottom thumb knob is all metal with a large base so that you can position a quick release plate underneath without wobbling.
If you choose to use the Loupe EX with a Swivel LCD camera extended (i.e. GH2 / 60D), they also sell a bracket for this to safely support the LCD from over extending.
The view finder is a solid choice amongst some of the other high end brand names, and is available for Canon, Nikon, and Panasonic GH1/GH2 cameras. Varavon also makes DSLR sliders, Cages, Video rigs, and other viewfinders. I'm extremely fond of their cage. Simple, ergonomical, functional, and lightweight. You can find more of those Varavon products available at B&H (click here).
Varavon Products - View Finders, Cages, Sliders, Rigs
And I didn't know it was available, but apparently they have almost all of their products on Amazon too (click here)