I used 3 hoya close-up filters (close up no1, close up no2 and close up no3 - found in my old camera bag alongside my old olympus gear!). These are old filters - no idea if they still make them, and no idea if they have different strengths. I suspect each filter is the same strength, so adding 3 together you get decent magnification. However, its hard to focus with them on (things get a bit soft) and you dont get much light - hence a tripod is a must... I shot at f22 to ensure most of the bowl and stamen were in focus, used light from the window.
I really want a proper macro lens - I think the results would be a lot sharper. But the close up filters are cheap so no complaints!