Thermal Johnson-Nyquist Noise Generator
These resistor circuits with instrumentation or op-amp amplifiers will all have biases due to bandwidth and frequency response and local electrical noise. You say you want to display on a scope. You want to see just a mass of noise or some sort of steps?

If you do not need really fast strings of numbers, you can not beat radioactive decay for randomness and it will not be affected by the environment. In fact, you can get them from a web site  http://www.fourmilab.ch/hotbits/  or use a Geiger counter. The scope could show spikes for each counter tick and they will be randomly spaced.

Bytes from the web site above you could use a simple microprocessor like an Arduino and display the output from a digital to analog converter. This will give random steps on the scope.

If you need to pursue the resistor (or diode or transistor) noise method, I can leave some links.