Try ebay or the classifieds, i have a 40mm front and back and got cool purple ones for £80 delivered off TMS, they're decent so far, but you can get them cheaper. Also i would reccomend 40mm rear, 45mm front, makes it look more even, mine sits just a tiny bit high on the front, with brand new shocks. Bit dont go lower than 45mm on standard shock absorbers.
40m front and back, like i said, it doesnt look that low at the front, but on a harsh corner it doesnt roll, mine lowers it but is almost solid after 25mm travel on the springs, meaning cornering is grrreat even bumps are pretty decent