A Hoya 48mm Lens shade for my Canonet QL17 G-III. Fits perfectly. Looks good too.

However, it' worth posting for posterity that the lowly Kalt 49mm threaded metal hood together with a 48-49mm step up ring makes an admirable substitute. In fact, this combo may be superior in that it creates a deeper, darker recess for the lens without any vignetting or metering issues. The only drawback is that it's slightly more viewfinder intrusive. But not too much.