How about a Vivitar macro-focusing teleconverter. A seven element unit built by Kiron. I have an article by Herb Keppler in Modern Photography in which he compares a Nikon 105mm f4 micro against a Nikon 50mm f1.4 and f1.8 lenses. His findings was that the f1.8 + teleconverter was the equal of the micro-Nikkor whilst the f1.4 wasn't far behind. Also a good 2x teleconverter. Uses a helicoid to move the 50mm lens away from the teleconverter section and goes from 1:10 to 1:1. I use mine with a Vivitar 135mm f2.8 Close Focusing lens for photographing butterdlies. They are cheap on ebay and would enable you try macro without spending a lot. There is also a Panagor version, also by Kiron, which moves elements inside the teleconverter to get to 1:1. Though it can't be used as a teleconverter.