Anyone catch the new CarrySpeed non-permanent NeoPrene swivel LCD mount to hold a View Finder? If you're not digging the Sticky Frame solutions, or the Quick Release Frame solution, then another option is this Swi-View. It slides in place over the LCD and held snug with a bit of velcro. Shown on a Canon 60D, but pretty much the same LCD as on the Canon T3i, so it should be compatible. Found via Amazon (click here) or via eBay (click here)
CarrySpeed Swi-View LCD ViewFinder Neoprene Adapter