Where can I find a comparator with the following attributes?
1. rail to rail inputs
2. at least 12 volts single supply.
3. 4 channels.
4. pdip or dip package for prototyping on solderless breadboard.
So far have only found 5 volt types.

 

LM339/LM2901 is a quad comparator, 2V-36V single supply, ±1V to ±18V dual supply.

 

LM339/LM2901 is a quad comparator, 2V-36V single supply, ±1V to ±18V dual supply.

Those don't have rail-rail inputs.

 

There are many comparators where common mode includes negative supply.

So can the circuit be changed just a little, so easily accessible components can be used?

Let's see a schematic of how the circuit should work.