A remote relative lived in the GDR and she did some private rebuilding. She wanted tiles in her bathroom so everyone she knew sufficiently well was asked to "find" tiles if they could.
After a few years she had all the tiles she needed.
"Finding" (scrounging, stealing, whatever ...) the grout to set the tiles was another matter so another relative who lived in the west was asked to buy grout in the west and bring it to the GDR.
My Grand Aunt lived in Leipzig. Each year, she was allowed to visit us after she retired. After Reunification we visited her in a Plattenbau in Leipzig. So I grew a quite good Saxonian accent during her visits.
Helping each other was quite common in East Germany. What the state factories could not deliver, somehow someone can "organize" it and you can swap for other things that you have "organzed".
One common practice was to send "Westpakete" (parcels with West German supplies). For example coffee, chocolate and fruits were commonly send. While the food supply in East Germany was quite good, frúits like bananas or oranges were sparse. A commom joke after the opening of the border was:
"How can you tell were the east side of the (Berlin) wall is?
Put a banana on the wall and where the banana is bitten of, there`s East Germany".