You could do it with an up/down binary counter (eg. CD4029) and a DAC (either an IC, or homemade R-2R ladder). I can't see the thread in your link, as I don't have an account, so I'm not sure if you want these voltages for signals, or for supplying power.
[Up/Down Pushbuttons]->[Debouncing*]->[Counter**]->[DAC]->[Op-amp/transistor and/or voltage regulator]
* Debounce with an RC filter and a schmitt trigger (Google)
** Check the datasheets, but I believe your counter will need some combinational logic to prevent pressing "down" at 1V from wrapping your output back to 5V, and pressing "up" at 5V from wrapping around to 1V. Pretty simple to fix both of these cases with some logic gates (down input to counter only triggers IF <button pushed> AND NOT <at lowest counting number>).
Of course, with a microcontroller, you can say goodbye to the debouncing hardware, the counter, any combo logic that might be needed, the DAC and remove the need for pull-up resistors. Doing it all in hardware is cooler and more educational though (IMO).