Hey! ...
hmmm well it's all do it yourself stuff ... it's not a kit of any sort
Digital Timer is from Orchard Supply Hardware
Jug is from the local pure water store
Air Pump , Airlines, and Air Check Valve is from Petco
Simply program the timer to whenever you want the pump to go on/off and it sends the air by airline (red) through the cap where it is sealed with aquarium sealer and builds pressure in the jug; pressure causes the water to escape through the other (green) airline and drip into your tank.
I am not sure what you mean by "will it fit in a 24g ..." the jug is pretty big and needs to sit by the tank or elsewhere depending on how much airline you want to run. You could possibly have everything in your bathroom or kitchen and run the airline to the tank.
In this picture I have the airline running to a gang valve which simply allows me to attach more containers by airline so if I wanted to dose something else I could do that as well by controlling where I am sending the air pressure.
Here you can kinda see the Air Check Valve suction cupped to the inside of my tank ...
Another shot ...
It's important NOT to have any reverse siphon or natural siphon happen or you'll top off all the water! It's easily prevented ... #1 don't put the air check valve or underwater #2 elevate the hose above the jug so the water has travel upwards before falling into the tank ... this way when pressure is lost the water cannot simply keep going