Shimano Ultegra STI Left Shifter Assembly
I know you can't buy spare parts, but if you cannibalize another shifter for parts, then this is how to put a left shifter back together. Click on the first thumbnail and navigate forward. Click on the picture for a high resolution image (you may have to use your browser's zoom feature to see it in full size.) Thanks to Dave at Music City Cycles (http://www.musiccitycycles.com) for his help and link to http://www.norvil.net/pedal/service/shimanosti/index.php (they have the start of disassembly for Ultegra and have full disassembly for Dura Ace)