IMHO, all drop checkers are the same, just pick one that you like the look of (and is in your price range).
the PH solution is bromo blue, same as what comes with most ph test kits. As for the reference solution se above (baking soda + water to make a dkh4 solution). This solution must be done accurately tho. Another option is to buy the solution locally, I know aquariums west in downtown has it (that's where I got mine).. else... check the sponsors on here
one more thing to consider is having more than one drop checker. sometimes you want to make sure your eniter tank is getting co2 evenly
