In my experience most parts of suspensions, axles and brakes are specific for this model (like rubber bushings, arms, dampers, damper carriers, brake calipers, etc.....), but find these parts, or motor parts too, is not a big problem, as they are made by other companies and they don't have to be necessarily OEM parts.
I basically mean small plastic parts, moldings, seals (doors, glasses......), interior parts like carpets, fabrics, linings, secure belts, etc...... My car is in overall "more than good" conditions, but I want her as perfect as possibile.
Glasses too are not easy to find, I'm looking for an OEM windscreen because mine has a little stone chip (repaired with resin, but still not perfect, and resinn comes off with years). I can find non OEM ones, but I want it with Skoda marks and codes like every other glass.
I bought a large supply of every plastic clips, I know exactly what kind of headache you're referring to 😄 but caged nuts are a good advice, thank you!