Get a smaller granny ring in 74mm bolt circle diameter. You should be able to go down to 26 or maybe even 24 with your current setup, just make sure your derailleurs have enough "real" capacity, as opposed to actual specified capacity, which is conservative to ease product support headaches. In other words, you'll probably be exceeding the allowed range for your front derailleur if you keep the 52 up front and reduce the size of the granny, but that is not likely a problem. Sheldon sez this should work fine, especially if you add a chain watcher to keep the chain from falling off the inside.