Marketplace
FRIBLK20FRIBLK22
Weatherproof Olympus macro flash. The flash heads are similar to the weatherproof FL-LM3, only there are two of them and with their own 4xAA power source.
Can be clipped on the included lens ring or freely positioned off it. Works with all the fancy Olympus macro focus stacking and hires shot stuff and can be a flash commander for other flashes. As far as I know works fine with the Panasonic M43 ecosystem stuff.
Use coupon FRIBLK22 at checkout.
Digidirect's ebay has been within a few bucks of this before but they don't seem to be right now.
Godox MF-12 should probably be considered as an alternative.
Need to also buy a trigger to work on those (though also good for other Godox flashes). Not weatherproof like the Olympus, but cheaper (even with the trigger) and you can use them as small flashes away from camera too (eg…product photography).
If I was going for something purely for my Olympus 60mm Macro, then I think the Olympus product would probably be superior. I have other Godox flashes though, and I'd be tempted by the MF-12's vs the Olympus, purely for the versatility.