You're going to have to invest in either some close up lenses (fit front of lens like a filter), a reversing ring (mounts your lens backwards on your camera), a reverse macro ring (connects two lenses together at the filter end), a set of extension tubes, or a bellows system.
The reverse rings will be the least expensive. The reverse macro ring lets you meter through the lens, with the reverse ring you'll have to compute the exposure.
Close up lenses may be the easiest solution, just mount like a filter and shoot. You can stack them (to a point), not sure what the minimum focus distance would be though.
Extension tubes or a bellows will get you right up there, though they are more expensive, especially the bellows.
Some of the dedicated macro lenses may focus that closely, but I've never used one so I really can't say.
hth
Jim