Instead of going with bar end shifters, you might want to consider looking for a set of Kelly Take-Offs (though these don't seem to be as easily available as they used to be). Then you can have the levers right by your hands when they're on the brakes. The thing I like about going that way is that you can use your current shifters and not have to worry about buying a new bar end or whatever (unless of course you decide you want to shift to indexing or something).