[Etsike]

Soviet economy worked in strange ways, since it was a plan-economy. So don't expect it to be structured like bike industry in the west. Every bicycle factory only had one (or very few) models it produced. And only on to produce road bikes was the factory in Kharkov. And often bicycles were a side product of factory which main product was something totally else.
If you really-really want a small frame from that era, then maybe you should consider a Erelikuas/Kreqzdute (smoke-sparrow in Lithuanian) produced by Vairas factory in Lithuanian SSR. And as you already understood, it's a youth bike. So it's single speed with coaster brake and such. Wheels aren't 700c but instead 533x35 originally, which basically gives you the same outer diameter for the whole wheel as the 26" (599) MTB rim with road tire on it. Also might have problems with installing caliper brakes, derailers and such. But the frame is quite lightweight at least. Especially when compared to Desna and Saljut, which seem to be made by engineers who also made tanks. Don't even think about dropout width, they all have flexible frames from soft steel, so you can just bend it easily.

And someone please correct me if I'm wrong by saying that there weren't such things as bicycle catalogues back then.