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mmm A step up adaptor (52-67) on the 52mm thread may be the cheapest choice (about 7$) otherwise the
POS-EP02 from Olympus ($42)...
The add-on "RING" is to help block light from the on-board flash from reflecting into the lens. This is less of a problem with a dome port than it is with a flat port. Many have used magic marker or black felt stuck to the lens to reduce the problem.
Phil Rudin