Varavon has a small line of Loupe EX view finders for cameras with swing out LCD screens. They have been available for cameras such as the GH1/GH2, or cameras with a 3.2" swing out LCD such as the Canon 60D, T3i, T4i, etc.
Here's a look at the latest Varavon Loupe EX specifically for the GH3 camera. This loupe bracket design allows you to take advantage of articulating LCD screens when positioning up or down while safely preventing any damage to the hinge. More information about Varavon's Loupe EX View Finders can be found at via eBay (here)
Varavon Loupe EX View Finder Articulating LCD Screens
FOR USA customers, some versions of the Varavon Loupe EX view finders can be found via B&H (here).
Varavon Loupe EX View Finders - via B&H