There is a SpeedBooster for the M-Series. I have one and works like a charm:
http://www.ebay.es/itm/EOS-EOSM-Focal-reducer-Auto-focus-adapter-EF-EFM-EF-to-EFM-EOS-to-EOSM-Booster/302171367352
Custom made in Korea EF to M. I'm attaching some sample pictures with a Canon 50mm 1.8.
The pics of the buildings are taken with the normal adaptor and with the speed booster
Diego Avendaño got a reaction from Michael Ma in Embarrassing threesome - Mini reviews of the Panasonic FZ2500, Sony RX100 V and Canon EOS M5