Well I use a system that is probably pretty easy to get materials and make. But you could just go buy it at your local grow store for $10.88
I use it on one of my tomato plants and it works great, I wish I could remember what it is, but it the concept is basically like siphoning gas out of a gas tank, you get some thin tubing and put one end with a hole half the size of a pot seed in a bucket full of water and the other end has some kind of cone thing you place in the dirt that is made out of some porous material that can let soak water into the soil. My tub for water that came with it is half a gallon and it lasts me for 2 weeks cuz it slowly leaks into the pot and the plant can utilize every bit of it all the time...the roots system around it is massive. It's the best description I can give you...very simple design. Maybe it can give you an idea for something or go look for it at the store.