Solidity - Generate unpredictable random number that does not depend on input

I know that the "how to generate random number" in solidity is a very common question. However, after reading the far majority on answers I did not find one to fit my case.

A short description of what I want to do is: I have a list of objects that each have a unique id, a number. I need to produce a list that contains 25% of those objects, randomly selected each time the function is called. The person calling the function cannot be depended on to provide input that will somehow influence predictably the resulting list.

The only answer I found that gives a secure random number was Here. However, it depends on input coming from the participants and it is meant to address a gambling scenario. I cannot use it in my implementation.

All other cases mention that the number generated is going to be predictable, and even some of those depend on a singular input to produce a single random number. Once again, does not help me.

Summarising, I need a function that will give me multiple, non-predictable, random numbers.

Thanks for any help.