How did people get highly specific things before the internet?

This may be too specific unfortunately. I was watching a video about the failed August coup attempt, in the USSR, in 1991. Boris Yeltsin was stood on a tank, holding a Russian flag. Not the Russian SSR flag, the modern Russian flag. Other people also had them.

Who made them? It was made of polyester, I doubt he made them himself, I’m confused as to how they were mass producing these flags, before Russia was a country, especially inside the USSR. Surely there wasn’t enough demand for these to be made and sold?

This got me thinking: how would you get specific items in an era before the internet. For reference, I was born deep into the internet era, so I’ve always been able to buy a pillowcase with my name on, or a tshirt with nick cage’s face, or whatever.