Sunlite also offers a threadless bottom bracket. It's cheap ($20-30), but I think you might need to chamfer one or both edges of the shell for it to seat properly.
Another option is to re-tap the bottom bracket to Italian threading, which has a slightly larger diameter. After tapping to Italian threading, just install any ol' Italian threaded bottom bracket. The small catch to this is that Italian bottom bracket shells are a little wider than English -- 70 mm versus 68 mm -- so you may need to use a thin spacer between the drive side cup and shell.