Extension tubes come to mind. You will lose your ability to focus to infinity (while the tube(s) are on, no biggie) but you will be able to focus MUCH closer to the lens.
Tubes are WAY cheaper than buying a dedicated macro lens.
I have no experience with auto-focus tubes, mine are strictly manual which works fine since I use my tubes with M lenses (m50/1.7 mostly).
Here's a shot of my keyboard's START key using my wife's k-m/jpg, about 62mm of extension tubes and my m50/1.7.
The tubes have no glass, therefore no image degradation.
Some here would know if you lose stops and the affect on DOF.
- Andrew