I'd say a Takumar should do well for you. They're already smaller than many other makes' normal lenses (non M42, like Minolta, Nikon, Canon). And Takumars render beautifully, IMO.
A smallish normal in M42 that is excellent is the Fujinon 55/1.8, which came with the ST 701 and other stop-down metering Fujicas. It's not the EBC Fujinon, which is the same lens with multicoating, but the EBC lens has a lug on the back of the aperture ring for open aperture metering, which might interfere with the body flange. It interferes on some cameras and not on others. I think it's OK on the SV.
I don't think even the Fujinon is going to make a great difference on the SV. The camera will still be most of the bulk.
If you were to have a compact SLR like one of the Fujica ST series, then it could make a real difference. A Pentax MX with an M series K-mount lens would be substantially smaller, as would an Olympus OM-1 with 50mm Zuiko. With M42, I'd say probably the Fujinons are the smallest.