If you already bought a refill kit and would like to try some cheaper inks, you can buy the ink in 125, 250 & 500ml bottles on this page. Extra tools, plugs etc available separately here.
You need to know your Canon ink cartridge numberto pick the right refill ink for it here...
Note: printers with two black ink tanks (eg. Canon iP4500/4600) use 2 different types of black ink (dye and pigment) ...they are not the same. You could use dye ink in both tanks, but you will lose the benefit of having the two black ink tanks & inks.